I happened to get a rebuilt 318 A of 1967 vintage for my sons truck. It has very low compression smog pistons in it and I am going to upgrade that. All the machine work is done on the block. It has the later cast crank. I don't like the little skinny rods in it which after checking are actually from a stock 273 or 318 two barrel. I got nosing around my shop and found a nodular iron cast crank from my magnum and a pair of forged 273 cranks. I am ordering some zero deck Pistons and going to use the magnum rods. I am curious what sort of power level the stock cast crank can handle. I am also wondering whether the magnum crank or the forged crank would be a better idea for this engine. I am mounting fully ported magnum heads and intake on this engine. My questions revolve around the bottom end. With a stud girdle that I will be installing, is the factory crank any good? Is the factory forged crank any better than the later magnum crank? I have built numerous small blocks, but they were always either with aftermarket cranks or with a 360. Advice here would be welcome.