I've just gotten a "new to me" car. I bought it "just for fun" and that part worked out really well - I don't know when I've had such a grin on my face, and I'd love to run it at Lincoln! Problem is, it's a BP Corvette. Locally, we still run BP as a regional class.
As nearly as I can decipher the rules, the modified floor pans and firewall make it illegal in XP, where it would otherwise more or less fit. I'm fairly sure it would be legal in E Modified, if laughably outgunned. I'm not terribly concerned about being competitive, I just want to have some fun with it.
I doubt if anyone would protest me in XP, as I'm likely to be dead last anyway, but if I run it at Nationals, I'd rather be legal.