A 151 S10 engine might be an option. I considered it, as I owned one for quite some time. Cross flow head, roller cam. The TBI intake I think could be easily adapted to a carburetor; as there is a lot of room under the injector, where the EGR get's dumped into a troth around the riser. It's also a water heated intake. I was told an early Monza distributor would swap to eliminate the computer controls. At one time a recall seeing adapters to mount to a turbo 350 trans. I assume they used a BOP bellhousing pattern, but I could be wrong. A Fiero high volume oil pump fits too. They had a rear sump pan as well. I considered swapping the crank for a longer stroke too. I was told it could be done, and I was told it couldn't be done. Take your pick! I don't recall the valve sizes, but it's probably possible to install bigger valves too. The only thing I noticed was the head casting looked as if the material didn't flow properly, on a similar one I had in a Buick. But it was not in a load bearing area, and it worked without a problem. I would think pistons, other than the stock dished ones could be found too. They had a 4 inch bore, if I remember right. The truck had an automatic with OD, although I don't know which one they used, but with 373 gears it was no slouch. Food for thought, if you can get one for next to nothing.