Power advantage between Ford 351, Mopar 340 and Chevy 350??

Like stated, I think the OP is interested in bore/stroke ratio comparisons. Once you change the cam, compression, valve size. It’s not the same engine as you started with. The true answer on which is “better” when it comes to getting EVERYTHING out of a 340 or 350 or 351 etc comes down to head flow. How much can you get out of the head with max effort port work. Most of the other parts will support a surprising amount of power. Again it’s no longer a 340 or 350 or 351.