I have a Chevrolet T56 in my 65 Barracuda. I put in a T5 before that and it had a factory A833 4 speed originally. 5th gear is fun from 60mph to 90mph and 6th gear is fun after that. 80mph is about 2000 rpm in 6th gear. The T5 shifts REALLY smooth, the T56 is a little more notchy but not much...