Chump cars are welcome at most clubs, but tend to just run in the closest appropriate class since there are rarely more than one of them at an event. Most clubs would happily give them a separate class if requested. The biggest issue with cars like this is they are often "mechanically deficient" (crap cans) and they break and/or leak frequently. This presents a much bigger problem in autox than it does at a crapcan race. Basically, don't bring your lemons car to an autox as a "shakedown" unless you want to piss off a lot of people. If you're confident you have a sorted car, you'll be welcome at pretty much all the clubs.