street class,
bonnet free
front bumper free
all other body panels must be metal (no carbon doors etc allowed)
roll cage free
suspension must use standard pick-up points, but adjustable arms, aftermarket dampers etc are allowed
car must run ABS if fitted with ABS as standard
drivers seat is free
must have either standard passenger seat or an approved type (ie no home made alluminium 2kg seats)
brakes are free
engine must be same type as from the factory (intake, turbo, exhaust, ecu etc are free)
car must ran approved semi slick tyres (and maybe consider restricting size for each model like in CT and IP, only a bit more generous than their sizes)
maybe consider making it that car must have current road registration. but I'm not 100% sold on that.