[1969 GMC]

One of the truck parts mags used to have 3.90's for the Eaton, but they were pricy. I don't think the D60 has a corresponding ratio, either. You can get 3.92's for a D44, iirc. Probably gotta go with 4.11's. From what I remember about the shafts, it depends. I test assembled mine and it fit, but I heard from some that you may need to cut about a 1/4" off the splined end.