Probably so. I don't know the year breakdown on the registers without searching. He should ask about balance. They either used a lot of mallory or they found 340 pistons that weigh around 570 grams instead of the 735g that the stockers do.
That's a big difference, yeah he called the guy and he is building him another motor to exchange it. I don't think I would trust him at this point. If he is a specialist that this guy claims he should have known this wouldn't work, then he told the guy that it was a 4 speed crank and he thought that what he was using, that's why it wont work.