Re: rear end questions
Why a 12 bolt? The truck 12 bolts are not significantly stronger than 10 bolts, actually have smaller pinions.
Axle shafts do not interchange 10 to 12 bolt.
2wd 1/2 tons 73-82 were 5 stud 12 bolts, there are tons of these in the j-yards. 6 bolts in 4wd for 10 or 12 bolts. Need to change U joints and may need metric to SAE brake pipe adaptor to swap complete axles.
Disc brakes are pricey but there are parts available (search this forum and the Suspension forum), costs about the same 10 or 12 bolt. Many kits available, or can piece together with a little thought.
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1987 2 ton 
1982  250/TH350 beater in progress
Dad's 1981  3/4 L6 3 on tree posi and no options, awaiting restoration or scrapping
Plus a mess o' tractors
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