5-speed would make for a much better performing car but driveshaft could be a problem, but many a/t's just happen to be almost the exact same lenght as a 5-speed! Autos are pretty interchangable on E-12's but some engines have a small hole in the end of the crankshaft and some have a large one. This is used as a locating device for the torque converter so the wrong setup won't work, but some large hole one's do have a bushing for the small pin torque convertor.