This an easy question. The answer, regional production.
As long as you do not get caught up in the stupidity that is National production car racing,regional production is a great play ground.
The dynamic is really simple, show up with your IT car with a fire system and the door glass removed. Take the green, stay running and continue to circulate around the track while watching the "real" production cars drop like Englishmen (apologies to the Brits) on a 95 degree humid day. Make sure that you avoid the oil and other bits dropped on the racing surface by faster cars than yours. Race against cars that should be much faster than you and beat them because although you are down 25 horsepower to them you know the line and understand how to carry speed into the corner and out.
Pull into impound and tell stories about fire, smoke, oil and parts falling off of other cars (sometimes all at once). Collect trophy later.

Shit, I just gave away all the secrets. Crap......

cheers
dave parker