I was planing on replacing my 66 BB turbo never been ported, with a 6466 BB but a friend was racing the car at the NMCA race at Norwalk and the transmission went out or the torque converter went south, Anyway a guy from Precision Turbo was at the race and my friend talked with him about my car and he said the 6766 would be a better pick for my car, I don't know if he was just talking going faster, It wouldn't hurt my feelings to go faster but I am really looking for a faster spooling turbo so it won't eat the transmission up boosting it so much going into the lights, He also said to replace the 3 inch down pipe with a 3 2/1, What I was wondering is do anyone know if the two turbo's spool about the same, Yes ,No, He also said make sure it is ported