I'm very happy with the 347 - has a little higher
oil consumption because of the stroke; (techies, feel free to correct me on this), one of the
oil rings sits over the wrist pin.
It dynoed at 383 Horsepower @ 5750 rpm, 414 ft-lbs torque @ 4000 rpm. This was at the flywheel, not on a chassis dyno.
The limitations are largely due to my choice of carburation - I have a Ford Tri-power setup on it. With a more modern intake and carb choice, my builder thought it would make an easy 425hp, if not more (he likes the Weiand Stealth intake and Holleys).
The other thing he likes to do is fill up the lower water passages with some type of epoxy/iron mix which combined with a stud girdle on the main bearings strengthens the block.
Very happy with the tranny choice; it would be nice to have an OD gear, but then I think the driving experience wouldn't be the same.