My car was a 4-speed originally. In so far as driving is concerned the 5-speed is big improvement. I did have to to do more transmission tunnel work than I would have prefered in order to get a good driveline angle. When it comes to shift quality the Tremec isn't bad, but I would give the edge to a well built 833 with Hurst linkage. "E" bodies and probably '71& '72 "B" bodies require an external linkage to operate the internal rails on the Tremec. Adding extra linkage has never improved shift quality in my experience. Even so it still shifts better than the T-5 in my Mustang which is similar in design to the TKO. As for durability I have 55,000 miles on mine. I shift at 6,200 rpm, but I certainly don't have the torque of a 500 cid big block.