are you goin to replace the axles also? if so then what ever posi carrier you choose will have to match the spline count of the axles..if your not gonna replace ya axles then youi have to find out your axle spline count so u can get the correct posi carrier...i belive stock gm axles are 28 spline but double check..but honestly i would get new axles cuz depending on your powere output..those old axles are now the weak point back there..u dont wanna break something and have to go back in there to fix it...