no,go back to 1967.You could of bought a heavy spec truck(cab&chassis;there is one in the pics section here on this web.truck is gray with red rims)this truck has or had the 10bolt,5hand hole ,7.25 bolt pattern rims.they bulit this up to 1972 then seized production in this since no one was buying it.that rear ens is the gm HO72 rear with different brake hubs.now trying to find something that was rear in the 60's ,now in 2010 is the same as finding james r. haffa.not happening.so we are looking for a easier solution to a expensive problem.
I looked at the pictures of that truck. It looks like something that probably had an Eaton HO72, but I can't count the lugs in those pictures and don't see anything else that would identify the rear under it. Those look like typical 16-inch 8-lug wheels to me.
Eaton made rears with 10-lugs but I don't believe they were ever put under 1-ton trucks.
I'd sure like to see a picture of the rear under your truck.