318 with a new 4” crankshaft.

Does KB still make hypereutectic pistons for that combo? I think if they still do they would use the less desirable thicker 5/64th size rings
Having done a stoker build on a 340, I would buy the kit instead of piecemeal like I did. Maybe check out protocol tom in the classifieds.
Get the forged crank. You will have to pay for balancing anyways, but you won't have to pay for heavy metal. I paid $350 for balancing, and $380 for heavy metal. I also used hypereutectic only because I thought they were light enough to not need metal added, but was wrong.