Crank as well. The block itself is fine. If your tearing down the motor and building hp, you can build a good motor by replacing all the weak internals.

East Coast B...I like speed as much as the next guy, but my boat is a 25' cabin cruiser. I'd be happy with 45 mph, and probably won't turn over 5000 rpm. I understand my Gen VI motor has its own balancer...if I knew that a 502 crank wouldn't mess up my balancing more than I already have, I'd keep an eye out for one. (I live at the end of the earth, so having an engine balanced is a nice fantasy).