I found one 4-53T in a 1978 GMC 6500, bought the truck on ebay and drove it home, then pulled the engine and parted and scrapped the rest. Another 4-53T came basically new as military surplus though I was a few owners after originally surplussed, picked it up in Texas. And another came from a skidder.
The Dana 70HD in my 2 ton came from burnt RV with a GM P30 chassis.
Grigg