V-6 rear thirds are the same (will bolt right into a 4cyl housing). they have slightly larger bearings and a little bigger pinion gear and the carrier is a different design and the third its self is beefier with more ribs on it than the 4 cyl. you can even fit 4 cyl gears in the v-6 third with a ring gear spacer and with the right combo of bearings you can fit v-6 gears into a 4 cyl housing.