I agree with Jim and the others advocating for an early ('54 -'55 1st series -- or a crate motor built later but out of the '54 mold) 261. Bolt-in, easy swap, easier rebuild, more power, etc.etc. If you really want a driver, I say skip the 235 and go for the 261. Coupled with Tim's recommendation for the rear ring and pinion swap, you'll have a vastly more driveable truck without losing the "old truck" feel and drive.
If you do all this, be sure to go through the truck's brakes and front end, too. Don't trust any of the previous owners/sellers/brokers -- it's *your* life to lose in an accident, not theirs.
