USRA rules can be viewed and/or downloaded here.

Exceptions:
(1) Aluminum bodies are permitted.
(2) Vado Speedway Park 360 rules permitted with four-barrel carburetor.
(3) 360 c.i. engines must run 7000 RPM chip. Anything bigger than 360 must run 6200 RPM chip.
(4) The LS 5.3-liter engine is permitted with 525 camshaft, MSD 6014 ignition box, stock rockers and cathedral port heads only. Electric fuel pump is permitted with pressure switch. May utilize a four-barrel crburetor and 7,000 rpm rev limiting device.
(5) No claims.
(6) Crank, crank gear and balancer must weigh a minimum 48 lbs.
(7) Any engine larger than 360 c.i. or more than 10.5:1 compression must run a 4412 and run a maximum of 6,200 RPMs.
(8) Any car required to run a two-barrel can only run the 4412 unaltered. A car that is allowed a four-barrel may run the Rochester two-barrel.

These mufflers are mandatory. Valid part numbers: 112530, 112535, 113035 and 14272735-78.