One can use a 400 block and put in a stoker crank. May be a bit more reliable. The smaller mains on the 400 allow for a better reving american Pontiac and less chance of a spun main. Also find a machine shop that knows Pontiac, not Chevys. Big difference on bearing clearances and also cam choices. Leason learned Pontiac engines don't work great on a Chevy style cam grind.

I use Lunati voodoo cams. Lots of torque.