[patrickt]

Ford changed the external balance for small blocks in 1980 from 28.2 ounces to 50 ounces. I believe the flywheels look the same, but you can not switch them without throwing your engine way out of balance. Trust me, you don't want to do that. What I am not clear on is whether or not there are aftermarket flywheels that are a different size, yet still maintain the proper external balance needed for your engine. I would think that if you held your new flywheel up against your old flywheel and there was an obvious size difference then there would be a corresponding balance difference as well -- but I don't know. That was one reason why I stroked my 428, it did away with the external balance issue.