4BT would have been MUCH BETTER, cheaper, gotten better economy, and been really cool, all while still using a GM trans..
6.5s only got 20mpg on a good day. where are you coming up with 12mpg more than they ever got? what kinda magic?
cause unless your 75 C10 weighs 2000 pounds, with the engine in it, then it will NEVER see 32mpg.
the 5.7 diesels got better economy than the 6.5 ever did, and those never got anywheres close to 32 mpg.
plain and simple, 32 mpg isnt gonna happen with a C10, 6.5TD, TH400, and 3.73 gears.. just not gonna happen.