Smells fishy to me. The first Grand national was in 82, and I think the first turbo turbo Regal was in 78. Prototype cars go for big bucks even though they can't be licensed so parting out a Grand National prototype just because it can't be licensed sounds fishy to me. Could be a prototype of some sort and GM decided to scrap it out and sell the parts, but it doesn't sound right. I would want to see good documentation.
