I don't know what bolt patteren the six speed has, or what tranny your car currently has.... Better check the torque rating for the tranny vs. the torque output of your engine, too. IMO your theory on more gears is correct...as for physically having room, probably but I'm sure the shifter location will be a bit different as the Vette trans shifter comes out of the top and the older style trannies have linkage bolted to the side of the tranny... Nothing real difficult, though. I've done the same thing putting 5 speeds in a number of projects from the muscle car era that originally came with a 4 speed..... Oh yeah, would imagine it will also require some crossmember mods, and maybe shoretening the driveshaft????