I believe you guys are right, 1960 was the first year of the 1/2T 4x4s and they were built by GM with Dana 44 axles. All previous were 3/4T Napco's. My '62 has a Timken 4 shaft transfercase, same thing was used in Duce-and-a-half's, it has provisions for a PTO to the rear and a second rear axle. Rockwell might be the same thing as Timken, I don't know about that. The transfercase was used with small mods for quite a few years after that, perhaps to 1970 or so. Eventually it was mated directly to the transmission. Mine is divorced, I am sure that is a holdover from the Napco "kits", no engineering required as with a mated case. I believe but have no data that the larger trucks used the very same setup with rear axle assemblies cut and knuckles added by Napco for the front and the same transfercase.
