I voted for "Anything you can drive on the street", but to me that means
street legal and I see a lot of cars in my area that have antique tags that are in NO WAY street legal. Slicks and open headers are NOT street legal. In Virginia NOS is ILLEGAL. It can be in the car, but has to be completely disconnected, not just unplugged. I see a lot of NOS setups in tagged/licensed cars too!! Now I do know some folks that drive 12:1 compression hot rods that need race fuel and they don't drive them far with race fuel costs, but they are street legal. I guess it's about what you want. I like to drive around and couldn't afford a race fuel car. My engine builder drives a N/A 9 second Plymouth Duster that is street legal in VA. No slicks. No NOS, full exhaust and full interior with roll cage. I don't think it quite runs 9's with street tires, but you get the point. It's all about what you want.
Matt B.