If it's the Pig type, and sounds like it is, 49 - 56 should be the same. I have run into an issue putting the later into a 54 Merc. Had to relieve the Housing a little to get the ring gear in. 3.78s, I tkink 3.36 ratio also, were usually from standard 3 spd ( non OD) cars.3.22s in most V8 auto...