I thought chassis and components were NASCAR supplier sourced as well. Certainly the acid dipped Penskes could be be considered tube framed silhouettes, as well.
That's why I think they should change their name to NAFCAR. Those cars are now nearly as "funny" as the nitro-burning floppers in drag racing!
See, that is the problem. The only relevant part of the name is Association of Automobile, which makes no sense at all.