[patrickt]

Your flywheel (M 6375 N427) looks just like my Centerforce aluminum flywheel, at least in your pictures and my memory. But if you go to either Summit or Jegs, both make a big deal about the M 6375 N427 not fitting pre-1965 Ford FE engines, but my Centerforce fits all FE engines, even back to 1963. I don't know why this would be, and what the difference even could be, but that's the only difference I can come up with. Maybe Brent knows what the pre-1965 thing is all about.