Thanks Tech. i figured it would be a "no go" or it would be common practice already.

I have been thinking about yanking the 283 and the 3 sp. and installing a strong 350, 383 or 400sb, along with a 4 speed Muncie.

Another question i have, unrelated to the original is final gear ratio on the 3 speed trans. the same as a 4 speed? (just trying to get a higher final ratio to run lower rpm at highway speeds etc.).

I dont want to go through the cost/trouble of putting a 4sp. in if the final drive ratio is the same as the 3sp.