Originally Posted by Jeeperz Creeperz
That's not completely true. The Dana 61 can use either a Dana 60 or a Dana 61 gear set. This is not to say that they are interchangeable, but rather some Dana 61's used a Dana 60 gear set, which could not be replaced with a Dana 61 gear set, and vice versa.
This is true up to a 4.56 according to Eaton, after that the carrier will not accept the 60 gear set.