Any one use the 440 source flywheels

So you need an externally balanced flywheel? (Not "neutral")
All I can tell you is that I bit the bullet and had Brewer's sell me one a new one.
They balanced it for a factory cast 440 motor and it worked like a charm.
People were not encouraging about just hanging a different flywheel on the motor.
But I figured this is done all the time with torque converter being swapped around, why not with a fly wheel?
Brewer's knows their stuff.
If I had a local machine shop drill a flywheel it might not have worked.