'65 and up were the modern axle set-up. '64 was the last of the tapered ones. However, it should be noted for the purpose of the OP's question, that if you are re-doing everything anyway (or the axle has already been converted), that a 62 or 63 "B" body housing is the narrowest one, and the '64 is a really wide one. '65 and later fall between those....
