Q:
A: That's a tough question because the first modification Nascar allowed was racing tires (for safety) back in the late 50's. In the 60's they were using modified production car's. Modified as in bigger brakes from trucks etc. since nobody was making racing stuff yet. They were still using production sheet metal, albeit modified, on purpose built chassis through the late 80's like the Monte SS's and Buick Regal's and T-Bird's etc. Once they started using FWD car bodies in the 90's like the Lumina the only thing stock was the hood, trunk and glass.