I'll tell you in the next day or two when my SFI flywheel comes in the mail (thanks to JEGS).
As of right now I have a 454 externally balanced. It had an externally balanced harmonic balancer, an internally balanced flywheel (for manual 4 speed tranny), and a counter balance weight (to make up for the zero balance flywheel). I am installing an automic so I needed a flexplate. I decided to go with a zero balance flexplate and use the counter balance weight as I will turn this into an internally balanced 489-496 someday down the road and didn't want to have to buy two different flywheels, plus I know the counterbalance won't change this way.