USRA Modified body rules

The nose is flat, parallel to the deck (the flat top of the body, which runs from the back of the engine to the tail) and never concave. (Rules 1.15.1, 1.12.2, Diagram F)

Nose

• Rule 1.15.1, Diagram N Nose width: 42 in max. (Rule 1.15.1, Diagram N)
• Rule 1.15.9, Diagram A1 Length. The front of the nose, plastic valance (the panel under the nose) included, can be no more than 42 in forward of the lower ball joint's center, no tolerance. Diagram A1 gives the same 42 in, from the center of the front wheel to the front of the nose. (Rule 1.15.9, Diagram A1)
• Rule 1.15.8, Diagram Q Ground clearance. Every nose piece part sits at least 5 in off the ground. (Rule 1.15.8, Diagram Q)
• Rules 1.15.2, 1.15.5, Diagram S Fins. You can run a fin of up to 2 in along each side of the nose, and the two fins must match. (Rules 1.15.2, 1.15.5, Diagram S)
• Rule 1.15.3 Fins can't reach past the leading edge of the radiator or past the leading edge of the hood. (Rule 1.15.3)
• Rule 1.15.5 What counts as nose. Anything between the fins is nose, and so is anything that separates from the hood. (Rule 1.15.5)
• Rules 1.15.6, 1.13 Plastic valances and plastic nose pieces are allowed. A plastic skirt (a strip along the bottom edge of a panel) of up to 5 in can go on the bottom of the nose piece. (Rules 1.15.6, 1.13)
• Rules 1.15.4, 1.15.7, 1.17.4 Aluminum and steel. Every bit of aluminum in the nose, fins included, sits completely inside the outer edges of the front bumper. No aluminum or steel outside the bumper. (Rules 1.15.4, 1.15.7, 1.17.4)
• Rule 1.15.7, Diagram V Plastic past the bumper. Rule 1.15.7 lets plastic extend outside the bumper as long as it stays within the nose measurements. Diagram V says the nose can't stick out past the front bumper. (Rule 1.15.7, Diagram V)

Bumpers

• Rule 1.17.2 Run a front and a rear bumper, both with rounded corners and no sharp edges. An official can turn away any bumper they judge unsuitable. (Rule 1.17.2)
• Rule 1.17.2 Bumper tubing: at least 1.25 in diameter with 0.065 in wall. (Rule 1.17.2)
• Rule 1.17.2 The top bar sits directly above the bottom bar, and the bumper has to carry the car if a tow vehicle lifts it. (Rule 1.17.2)
• Rule 1.17.1, Diagram T Bumper center height: 16 to 20 in off the ground, front and rear. (Rule 1.17.1, Diagram T)
• Rule 1.17.2 Mount the front bumper from one frame end to the other, with its bottom loop parallel to the ground. (Rule 1.17.2)
• Rule 1.17.5 Front bumper width: 46 in max, outside to outside. (Rule 1.17.5)
• Rule 1.17.6, Diagram A1 The front bumper sits no farther forward than 42 in from the center of the lower ball joints, the same mark as the nose. (Rule 1.17.6, Diagram A1)
• Rules 1.17.3, 14.5.4 The rear bumper also guards the fuel cell (see Deck and spoiler), and ballast can't be attached to it. (Rules 1.17.3, 14.5.4)

The hood is flat from side to side and runs level or slopes down toward the nose. (Rule 1.7)

Hood

• Rule 1.7 No reverse rake (a hood that rises toward the nose), no bowed or concave hood and no lips along its sides. (Rule 1.7)
• Rule 1.7 The back of the hood sits no more than 2 in above the deck and is sealed off completely. (Rule 1.7)
• Diagram I Hood sides: 6 in max on the vertical sides. (Diagram I)
• Diagram M Hood item M: 6 in max. Diagram M marks a raised piece on top of the hood, drawn as a scoop, and doesn't name the part. (Diagram M)
• Rule 2.9 Brace bars ahead of the roll cage can't sit higher than the "stock hood height". (Rule 2.9)

• Rule 13.1.4 Radiators and oil coolers can't stick up above the interior. (Rule 13.1.4)

Engine covers

• Rule 1.9 You can fit engine covers or panels ahead of the door, next to the engine compartment, if they stay at least 6 in from the door, measured side to side. (Rule 1.9)
• Rule 1.9 Leave one side open so officials can look at the engine on the scales. (Rule 1.9)

Engine placement

• Rules 3.11, 13.1.5 Engine setback: the rear of the engine (the bell housing flange) at least 72 in ahead of the rear axle centerline, no tolerance. (Rules 3.11, 13.1.5)
• Rule 13.1.6 Offset: the front and the rear of the engine each within 2 in of the centerline of the front crossmember. (Rule 13.1.6)
• Rules 13.1.6, 1.12.4 Keep the engine square in the chassis, or skew its rear to the left only. Either way, the deck still has to meet its 4 in skew limit (see Deck and spoiler). (Rules 13.1.6, 1.12.4)
• Rule 13.1.7 Crankshaft height: the front center of the crank at least 11 in off the ground. (Rule 13.1.7)
• Rule 13.1.10 Mount the radiator ahead of the engine. (Rule 13.1.10)
• Rule 13.1.5 Any American make of engine can be used. (Rule 13.1.5)

The tops of the doors and quarter panels (the body sides behind the doors) sit no more than 1 in above the deck, the same on both sides, no tolerance. (Rule 1.13)

Doors and quarter panels

• Rule 1.13, Diagram C1 Door and quarter panel height: no more than 37 in of total material. Diagram C1 also sets a 22 in minimum for the doors. (Rule 1.13, Diagram C1)
• Rule 1.14, Diagram F Leaving out the hood and nose, the top of the body starts no farther forward than the back of the engine block. Diagram F shows the top of the door and the deck starting there. (Rule 1.14, Diagram F)
• Rule 1.14, Diagram G The bottom of the body (the door) can reach up to 8 in ahead of the back of the engine block. (Rule 1.14, Diagram G)
• Rule 1.13 Rear quarter panels keep a standard size wheel opening. (Rule 1.13)
• Rule 1.13 The rear edge of each quarter panel is square to its top edge, and it can't run past the rear of the deck or tuck under it. (Rule 1.13)
• Rule 1.1 Doors and rear quarters can be fire-retardant plastic or composite (see Body and panels). (Rule 1.1)
• Rules 1.16.5, 1.16.6 No fins, wings, lips, deflectors or other air spoilers beyond the ones the rulebook allows, and each allowed one matches its partner on the other side. (Rules 1.16.5, 1.16.6)
• Rule 1.16.5 Panel break: up to 0.5 in, bent into a body panel for stiffness. (Rule 1.16.5)
• Rule 13.1.11 No exhaust through body panels or fenders. (Rule 13.1.11)

Skirts and ground clearance

• Rule 1.13, Diagram P Plastic skirt: up to 5 in on the bottom of the doors, quarter panels and nose piece. (Rule 1.13, Diagram P)
• Diagram *** The lowest point of the body sits at least 3 in off the ground. (Diagram ***)

Car width

• Rules 1.11, 3.10 Car width: 80 in max, front or rear, measured between the widest points on each side, no tolerance. The only part allowed past 80 in is the door ahead of the left rear tire, for tire clearance. (Rules 1.11, 3.10)
• Rule 8.1.8 Wheel spacers count toward the 80 in. A spacer between hub and wheel must be aluminum. (Rule 8.1.8)

Door bars and door plate

• Rule 2.1 Driver side: at least 3 door bars (the horizontal cage tubes beside the driver), parallel to the ground and square to the driver, welded to the cage at the front and the rear. They have to protect the driver without making it unduly hard to get in or out. (Rule 2.1)
• Rule 2.1 Driver-side door bars and uprights: at least 1.5 in diameter with 0.083 in wall. (Rule 2.1)
• Rule 2.1 Door plate: steel, at least 18-gauge (0.049 in), welded securely to the outside of the driver-side door bars. It covers from the top door bar to the bottom door bar, and from the rear hoop down post to 5 in ahead of the seat. (Rule 2.1)
• Rule 2.1 Passenger side: at least 1 cross bar, horizontal or angled, of at least 1.25 in OD with 0.083 in wall, plus 1 top horizontal bar of at least 1.5 in OD with 0.083 in wall. (Rule 2.1)

The roof follows the deck: keep its line parallel to the deck, front to back and side to side, with up to 5 in of slope from rear to front. (Rule 1.5)

Roof

• Diagram * Diagram * checks the roof with a level: no more than 5 in of clearance at the front and 2 in at the back. (Diagram *)
• Rule 1.5 Front edge: a downturned roll of up to 2 in. (Rule 1.5)
• Rule 1.5 Rear edge: a stiffener of up to 1 in, turned down square to the ground, and no more than 4 fasteners. (Rule 1.5)
• Rule 1.5 Side edges: a 1 in lip is allowed on the left and right edges. Vertical sides on the roof: 4 in max. (Rule 1.5)
• Rule 1.5 Aluminum roofs are allowed, kept flat and never concave. (Rule 1.5)
• Diagrams K, L Roof length: 40 to 56 in. Roof width: 44 to 50 in. (Diagrams K, L)
• Rule 1.5, Diagram C2 Car height: 56 in max, measured from the ground to the car's highest point. (Rule 1.5, Diagram C2)

Pillars and windshield

• Rule 1.2 Front window supports. The posts on each side of the windshield opening have to look like a production car's. A painted roll bar doesn't count. (Rule 1.2)
• Rule 1.2, Diagram R Each support is no more than 20 in at the bottom of the windshield opening and runs straight up to the top. Both sides match. (Rule 1.2, Diagram R)

• Rule 1.4 The windshield opening and its corner posts keep a standard shape, with no streamlining across the top. (Rule 1.4)
• Rule 1.3 Half windshield: an aluminum half windshield is allowed on the driver's side of the front opening only, reaching no more than 6 in past the steering wheel. (Rule 1.3)
• Rule 2.7 A screen or bars are required in the front window opening, in front of the driver's face. (Rule 2.7)

Windows

• Rule 1.3 Window openings: every opening, front, back, left and right, at least 12 in. (Rule 1.3)
• Diagram H Side window opening: 12 to 18 in tall. (Diagram H)

Sail panels

• Rule 1.6, Diagram O Sail panels (the side panels running from the roof back to the deck) can be solid or open, with the same design and style on both sides. (Rule 1.6, Diagram O)
• Rule 1.6 An open panel needs a border at least 2 in wide. (Rule 1.6)
• Rule 1.6 Length: from the back of the driver's seat rearward, reaching to within 3 in of the spoiler support. (Rule 1.6)
• Rule 1.6 An open panel can end at the spoiler support's front edge or ahead of it, never behind it. A solid panel can run to the rear edge of the deck but not past it. (Rule 1.6)
• Rule 1.6 Height: the top sits no more than 8 in above the back edge of the deck. (Rule 1.6)
• Rule 1.6 Front edge radius: 3 in max. (Rule 1.6)
• Rule 1.6 Shape: an even outward bow of up to 4 in top to bottom, never concave, and an even arc of up to 3 in along the top, front to back. (Rule 1.6)
• Rule 1.6 Mounting: within 1 in of the outer edge of the deck, flush with the top of the deck and with the outer edge of the roof. (Rule 1.6)
• Rule 1.6 Left against right: the top-to-bottom bow matches, or else the material length from roof line to deck differs by no more than 5 in. (Rule 1.6)
• Rules 1.16.3, 4.6.3 The spoiler and the seat back each have a rule tied to the sail panels: see Spoiler and Seat position. (Rules 1.16.3, 4.6.3)

Window net

• Rule 15.13 A full-size window net is required in the driver's window opening on the left side, with its mounts welded or securely bolted to the roll cage. (Rule 15.13)
• Rule 15.13 Recommended: approved racing arm restraints. (Rule 15.13)
• Rule 15.13 Recommended: weld or bolt the net mounts to the inside of the main cage, on top. (Rule 15.13)

Skin the rear of the deck over completely, with no open trunk area. (Rule 1.12.1)

Deck

• Rule 1.12.2, Diagram E Deck length: 120 in max, from the rear of the engine to the rear of the deck. (Rule 1.12.2, Diagram E)
• Rule 1.12.3, Diagram D Deck height: 39 in max off the ground, no tolerance. (Rule 1.12.3, Diagram D)
• Rule 1.12.4, Diagram J Deck width: 53 to 66 in, the same at the front and the back. (Rule 1.12.4, Diagram J)
• Rule 1.12.4, Diagram W Square or skewed. Keep the front edge of the deck level side to side. Run the deck parallel to the frame, or skew it to the right: draw a line from the front of the deck parallel to the engine, and at the rear of the deck the deck can sit up to 4 in right of that line. (Rule 1.12.4, Diagram W)
• Rule 1.12.6, Diagram U Flat side to side and front to rear, never concave. Diagram U makes the cockpit the exception side to side. (Rule 1.12.6, Diagram U)
• Rule 1.12.5, Diagram U Slope: rule 1.12.5 allows 8 in of total slope and caps the slope from the driver's seat to the rear of the deck at 4 in, measured from the ground, on every car. Diagram U allows up to 8 in of rake front to rear and applies the 4 in cap, from the back of the seat to the rear of the deck, only when the doors are flat. (Rule 1.12.5, Diagram U)

Spoiler

• Rule 1.16.1 Spoiler height is the complete material height, counting the hinge and all the hardware that joins the spoiler to the deck. (Rule 1.16.1)
• Rules 1.16.1, 13.3, 13.3.3, 13.6, 13.6.1 5 in max: the USMTS/USRA spec engine, the 23-degree steel-headed flat tappet engine or the open engine (option 4: any engine not listed in the other options). (Rules 1.16.1, 13.3, 13.3.3, 13.6, 13.6.1)
• Rules 1.16.1, 13.4, 13.5.2 6 in max: the USMTS/USRA concept engine or a properly sealed GM CT525 crate engine. (Rules 1.16.1, 13.4, 13.5.2)
• Rules 1.16.1, 13.5, 13.5.1 7 in max: a properly sealed GM 604 crate engine. (Rules 1.16.1, 13.5, 13.5.1)

• Rule 1.16.2 The spoiler runs in a straight line from the right edge of the deck to the left edge, flush to the deck and no wider than the deck. (Rule 1.16.2)
• Rule 1.16.2 Keep the spoiler material flat. One stiffener of up to 1 in is allowed on its back side. (Rule 1.16.2)
• Rule 1.16.3 Keep the spoiler separate from the sail panels. (Rule 1.16.3)

Spoiler supports

• Rule 1.16.4 Up to 2 center supports and 2 side supports can attach to the front of the spoiler, all the same shape. (Rule 1.16.4)
• Rule 1.16.4, Diagram B2 Support length along the deck: 20 in max. (Rule 1.16.4, Diagram B2)
• Rule 1.16.4, Diagrams B1, B3 Support height above the deck: 4 in max at the front edge and 8 in max at the back edge. (Rule 1.16.4, Diagrams B1, B3)
• Rule 1.16.4 Flat top edge of a support, from the end of its front slope to its back edge: 10 in max. (Rule 1.16.4)
• Rule 1.16.4 A support can reach no more than 2 in behind the spoiler. (Rule 1.16.4)
• Rule 1.16.1, Diagram B1 Diagram B1's 8 in support height is taller than the 5, 6 or 7 in that rule 1.16.1 allows for the spoiler with all its mounting hardware. (Rule 1.16.1, Diagram B1)

Fuel cell

• Rule 7.4.1 Use a commercially made fuel cell, held by at least 2 steel straps that are 2 in wide at every measuring point. (Rule 7.4.1)
• Rule 7.4.2 Enclose the cell in a steel container. Behind the axle, protect it with securely mounted roll cage tubing. (Rule 7.4.2)
• Rule 7.4.3 Fuel cell height: the lowest point of the cell at least 10 in off the ground, and no part of it lower than the protective tubing. (Rule 7.4.3)
• Rule 7.4.3 Fuel cell guard: the protective tubing can be no wider than 6 in on each side. (Rule 7.4.3)

• Rules 7.4.4, 7.4.6 Check valves are required. A cell without a positive-seal filler neck and cap needs a ball-type, flapper, spring or filler rollover valve. (Rules 7.4.4, 7.4.6)
• Rule 7.4.5 Capacity: no more than 32 gallons. (Rule 7.4.5)
• Rule 1.17.3 The rear bumper can be round tubing, and it must protect the fuel cell. (Rule 1.17.3)

The floor and the firewall both have to be complete across the driver's compartment. (Rule 4.4)

Firewall and floor

• Rule 4.4 Floor pan: at least 0.125 in aluminum or 0.06 in steel, covering the whole driver's compartment. (Rule 4.4)
• Rules 4.4, 15.15 Firewall: the rulebook gives no metal or thickness for it, but it can't be plastic. Plastic is allowed only from the firewall's edge out to the body skin (see Body and panels for the other places plastic is allowed). (Rules 4.4, 15.15)

Interior sheet metal

• Rule 4.4 From the top of the driveshaft tunnel, cockpit sheet metal runs level across to the right-side door bars, or angles up to the top of those bars. (Rule 4.4)
• Rule 4.4 No interior sheet metal can sit higher than a standard window opening or close one in. (Rule 4.4)
• Rule 4.4, Diagram ** The driver must be able to get out on both sides, and officials can ask the driver to climb out wearing the helmet. (Rule 4.4, Diagram **)

Seat position

• Rules 4.6, 4.6.3 Install the seat properly. The seat back can't sit behind the front edge of the sail panel. (Rules 4.6, 4.6.3)

Cage-to-body fit

• Rule 2.1 Cage tubing: the main four-point cage is continuous hoops of round steel tubing, at least 1.5 in diameter with 0.095 in wall, and officials have to accept it. (Rule 2.1)
• Rule 2.1 Tubing of 1.75 in diameter needs at least 0.083 in wall; tubing under 1.75 in needs at least 0.095 in wall. (Rule 2.1)
• Rule 2.1 No sliding or slip-joint unions in the main cage. (Rule 2.1)
• Rule 2.5 Build the cage from front and rear hoops joined by side tubing, or from side hoops, all at the tubing sizes above. (Rule 2.5)
• Rule 2.4 Cage mounts: mount the cage to the frame in at least 6 places. (Rule 2.4)
• Rule 2.6 With the helmet on and the driver belted into the seat, the top of the driver's head can't stick up above the cage. The halo (the top hoop over the driver) needs a cross bar. (Rule 2.6)
• Rule 2.8 Foot protection. Required: a bar across the back of the engine, plus vertical bars and rub rails (strips along the body side that take contact) or similar protection. (Rule 2.8)
• Rules 2.2, 15.13 Pad every roll bar within the driver's reach with a material officials accept, and every bar around the driver with approved roll bar padding. (Rules 2.2, 15.13)
• Rule 2.2 Recommended: fire-retardant padding. (Rule 2.2)
• Rule 2.10 No adjustable bars on the frame or the cage. Removable bars are allowed. (Rule 2.10)
• Rules 2.3, 2.11 Officials have to accept the cage's installation and workmanship. A cage that breaks these rules can draw cash fines and other penalties. (Rules 2.3, 2.11)

A Modified is built on a factory frame from a 1960-or-newer American passenger car, and the rules below say where you can cut it and what you can change. (Rule 3.1)

Cars today are usually built on a factory front stub (the front section of a frame, ahead of the firewall), cut behind the engine, with the rest of the chassis fabricated by a chassis builder.

Which frame

• Rule 3.1 Starting frame. It has to be a factory production full-perimeter frame (a separate frame that runs around the car under the body) with parallel rails. (Rule 3.1)
• Rules 3.1, 3.9 Front stub. The front of the car stays on that factory frame. Tubular front clips (a front stub built from tubing) aren't allowed. (Rules 3.1, 3.9)
• Rules 3.1, 3.3 Rear section. You can cut the factory frame off at the rear, even with the rear of the engine or farther back, and build the rest. Every frame part, factory or built, is steel and properly welded. (Rules 3.1, 3.3)
• Rule 3.4 Both sides. The frame stays full and complete on both sides and able to carry the roll cage on both sides. It is never widened or narrowed. (Rule 3.4)

Allowed frame changes

• Rules 3.2, 3.6 Apart from the cut, change the frame only to install springs and shocks. The rear can be reworked to take leaf or coil springs. (Rules 3.2, 3.6)
• Rules 3.1, 3.4 On the factory frame you keep ahead of the cut, every factory hole stays in place for inspection. (Rules 3.1, 3.4)
• Rule 3.4 Every frame measurement must meet the tolerances on USRA's frame diagram sheet. Any measurement the sheet doesn't list stays within 0.5 in either way of OEM (the original factory figure), no tolerance. (Rule 3.4)

• Rule 3.4 The sheet is drawn on a 1968-1972 GM Chevelle frame. On it, front frame width, from the centerline of the front stub to the outside of each rail, is 27.5 to 28.25 in on each side (sheet item C). (Rule 3.4)

Hanging the body

• Rule 1.13 Every body panel stays outside the outer frame rails. (Rule 1.13)
• Rule 1.12.4 The deck lines up with the frame and chassis, or skews to the right within the limit under Deck and spoiler. (Rule 1.12.4)

Wheelbase and ride height

• Rule 3.8, Diagram A2 Wheelbase: 108 in min on both sides, front axle center to rear axle center, no tolerance. (Rule 3.8, Diagram A2)
• Rule 3.5 Right front rail. The right outer front rail stays at factory height and is never raised. It's checked with frame sheet item L: measure from the bottom of the marked frame hole to the ground and from the bottom of the frame to the ground; the two differ by 5.5 to 6.5 in, nominally 6 in. (Rule 3.5)
• Rules 3.5, 5.5, 5.5.7, Diagram *** Front frame height: the front of the frame sits between 4 and 7.5 in off the ground, no tolerance, with the front crossmember exempt. Diagram *** gives the same 4 in minimum for the frame. (Rules 3.5, 5.5, 5.5.7, Diagram ***)

Weight and ballast

• Rule 14.1 The car is weighed after the event with the driver aboard in full racing gear. At events that run more laps than usual, officials can set a burn-off allowance before the event starts. (Rule 14.1)
• Rules 14.3, 14.3.1, 14.3.3 Minimum weight with a USMTS/USRA spec engine, the 23-degree steel-headed flat tappet or a GM CT525 crate: 2,450 lb. (Rules 14.3, 14.3.1, 14.3.3)
• Rules 14.3.2, 14.3.3 Minimum weight with the USMTS/USRA concept engine or a GM 604 crate: 2,400 lb. (Rules 14.3.2, 14.3.3)
• Rule 14.3.4 Minimum weight with the open engine: 2,500 lb. (Rule 14.3.4)
• Rules 13.6.2, 14.3.4 Open engine with aluminum heads: carry at least 25 lb of weight ahead of the mid-plate (the plate at the rear engine mount). (Rules 13.6.2, 14.3.4)
• Rules 13.1.2, 14.4 Lightened block (material removed inside or outside), any engine: add an extra 25 lb ahead of the mid-plate. (Rules 13.1.2, 14.4)
• Rules 14.5, 14.5.1 No ballast in the cockpit or on any rotating or suspension part, and none outside the body or hood area. (Rules 14.5, 14.5.1)
• Rule 14.5.4 Ballast attaches only to the frame, the roll cage or the rear-end housing, never the rear bumper. (Rule 14.5.4)
• Rule 14.5.2 Mount it securely, paint it white and mark it clearly with the car number. (Rule 14.5.2)
• Rule 14.5.3 Bolt ballast on with at least 2 bolts of 0.5 in per 100 lb or less of ballast. A piece of 25 lb or less can hang on 1 bolt of 0.5 in. (Rule 14.5.3)

Under the car

• Rule 1.8 No belly pans. The rulebook counts any object or material that changes the airflow under the car as a belly pan. (Rule 1.8)
• Rule 1.8 A rock shield is allowed to guard the oil pan and the underside of the motor, running from the front crossmember back no farther than the rear engine mount (mid-plate), and no wider than the radiator. (Rule 1.8)
• Rules 6.1, 6.1.1 Mount the battery securely and covered, inside the frame rails. (Rules 6.1, 6.1.1)
• Rule 6.1.1 If the battery box sits outside a frame rail, put a nerf bar (a protective tube bar) around it, of tubing at least 1.25 outside diameter. For the wall minimum, the rule's words say ninety-three hundredths (0.93) and its digits say 0.093, and it gives no unit for either size. (Rule 6.1.1)

The rulebook names no body style or approved body kits for this class, so you build the body to the shapes and measurements in the topics above.

Panel materials

• Rules 1.5, 1.15.4, 1.15.7 Metal: the rulebook names no metal for the body panels. For aluminum in the roof and metal in the nose, see Roof, windows and sail panels and Nose and bumpers. (Rules 1.5, 1.15.4, 1.15.7)
• Rule 1.1 No plastic or composite body panels, except the doors and rear quarter panels, which can be fire-retardant plastic or composite. (Rule 1.1)
• Rules 1.13, 1.15.6 Plastic is also allowed for the nose piece and nose valance (see Nose and bumpers) and for the bottom skirts on the doors, quarter panels and nose piece (see Doors and sides). (Rules 1.13, 1.15.6)
• Rule 15.15 Apart from those plastic parts, no plastic anywhere except from the edge of the firewall to the body skin and from the inner wheel tub to the body skin. (Rule 15.15)

Damage

• Rule 1.10 Officials can keep a car with excessive body damage from racing. (Rule 1.10)

Numbers and appearance

• Rules 1.18, 1.18.1 Numbers. Every car carries large, readable numbers on both sides, on the roof, on the nose and on the rear panels. (Rules 1.18, 1.18.1)
• Rule 1.18.1 Side numbers. These should contrast with the body color and be at least 18 in tall and 4 in thick (the width of each stroke). (Rule 1.18.1)
• Rule 1.18.1 Roof numbers. These should be at least 24 in tall and 4 in thick. (Rule 1.18.1)
• Rule 14.2 Weight number: post the weight the car will run at on the left windshield post, 2 in tall, in a color that contrasts with the car. (Rule 14.2)
• Rules 14.2, 14.3.4 A car with no weight posted has to weigh the heaviest minimum in the class, 2,500 lb (the open engine figure), and still carry any added weight the class calls for, where it calls for it. (Rules 14.2, 14.3.4)
• Rule 1.18.2 Advertising. Officials can assign, approve or turn down any advertising, sponsorship or similar deal tied to an event, for the public image of the sport or of USRA. (Rule 1.18.2)
• Rule 1.18.2 Neat cars. Every car must look neat, and officials approve each car to race. By racing, you agree to follow their decisions on this. (Rule 1.18.2)