aggie john, the same rear end was used through 1972 in 3/4 & 1 ton trucks. 1 tons in the 50s usually had 5.14s. 3/4 tons with 6 cyl. usually had 4.57s. 67-72 3/4 tons with V8s (especially auto trans equipped) usually had 4.10s. if you find a 67-72 truck with 4.10 gears that's in good shape (& they usually are) & doesn't have to much slack, you can just swap in the whole 3rd member & not worry about setting up the gears. If you do happen to only come up with the ring & pinion gears, get a factory service manual for AD trucks & it gives step by step Instructions for disassembly & reassembly of the 3rd member. setting up r&p gears & rebuilding manual transmissions is not rocket science or some kind of black art. If you can do a brake job or rebuild a carb. you can do it. the only special tools needed are a dial indicator & you could make something for those oddball looking wrenches in the manual for adjusting the carrier bearings, or just use a hammer & punch for that.
I've just done this swap On my 50 3800 & love it. I run 60 & 65 on the highway no problem. granny low can't tell the difference, it'll still practically climb a tree @ idle!
