You can make them street legal and get plates for them, I've seen altereds do it.
People tend to get really butthurt over the words "street car" it seems. A street car is just that, something that can get tags and be insured to drive on the street.
Now, how WELL your car drives on the street is up to you. That is why True Street has the cruise, that keeps a "street legal" race car from getting in.
I have seen first hand guys try to sneak something like that into a True Street race and end up getting stuck on the side of the road