This page may be of help:
Flywheel patterns for the clutch Now, when I had my FE built, I had it internally balanced because the SCAT stroker crank made that easy on my 428 block. The builder balanced my pressure plate, by welding a small chunk of metal, with the neutral balanced flywheel (which, of course, is never perfectly neutral) and marked both with a little, easy to line up, "X" -- that's the traditional way to do it. If you're going to the trouble of building a nice FE, you'll want to balance your clutch with your flywheel, but there are different bolt patterns and they all have to line up.