what does it matter if it s a stock diff? mine has a dana 60 semi float with 456s,seems to be geared nice,more of a puller than a racer,tons of torque,. the air locker (arb) operates between 80-110 psi so cold diff might be an issue.will crown and pinion from dana 60 semi float fit in to a dana 60 full float.will be putting the full float in this summer.i think the 489s would be to low,411s would be nice if you dont pull huge loads. the compressor is very small it will fit in the front or floor.the locker lets you choose between locked diff or unlocked diff by flipping a switch,so not turning is not an issue ..