Counterfeit Cars on FABO!!!

So to the guy that pulls home a rust bucket... Start replacing panels with donar car panels. Even after all his effort and blood and sweet is his car still not a 340 car because the panels came from a /6? Assuming everything around the VIN is replaced how far does one have to go to keep it numbers matching? Considering the bodies are the bodies are just about the same regardless of engine and drive train package.