A carbureted Chevy V6 with a 4 barrel like Mercruiser Marine ran might be a good option- - - -it was a hotrodded version of the engine a lot of the S-10 pickups ran, it has the V8 bellhousing bolt pattern, and they were available with a 700R4 transmission. Mercruiser ran a pretty radical cam, and that cam is still available on Ebay and elsewhere. A V6 is an oddball swap for the old Chevy trucks, but it's definitely an overlooked option, IMHO.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!