Once again I'll assume you are refering to the real street cars class(dot) and not the crazy 2000 hp funnycar looking things that run heads up.
Most real street car classes are raced on a bracket. handicapping the slower car. So you wont have to worry about losing to the guy with the deepest pockets, call the trackand do some research. That will be your easiest way to determine what class is best for you.
Goodluck, Charles