If you don't have a problem with swapping your original stuff, I'd go with later drivetrain. There were some defintite improvements in the 50's and 60's. Parts are a little easier to come by. I can still get most parts at Autozone or Napa. A mid 50's-early 60's 235 would be a good choice or a 60's 250 or 292. You could pretty much have your choice of tranny's with these.
I'd find a newer rear which different size ring and pinions are still made.
You're gonna get better performance and driveability from a newer drivetrain and more parts will be available for upgrades in the future.
It might cost more than the '39 Chevy stuff initially but, in the long run, it'll more than pay for itself.
-David
Kustoms-and-Sleds
