My club has a coupe class for '60s and early '70s NASCAR modifieds. Those can use T-Jet or A/FX chassis, beyond that almost anything goes. The A/FX cars usually handle better, but you have to cut the body mounting ears off.

At one time we raced Tyco and Lifelike M chassis cars with Lexan NASCAR SK Modified/Featherlite bodies.

Now we have a class for Aurora Magnatraction and JL X-Traction cars with Whelen Modified bodies.
