As you are probably aware, stock Pontiac engines use the flywheel as part of the internal balancing. Therefore, stock flywheels (and flexplates) are manufactured with an imbalance built in to them to equal out missing internal balance. This means that you can throw away a damaged flexplate and run down and purchase a new one and things will be great when you install it "as-is".
As you get up into higher horsepower rebuilds, one of the practices is to internally balance the engine with heavy metal to a "zero balance" state. You then also zero balance the flexplate since the imbalance is no longer needed, and it would actually do harm if not corrected.
So what it comes down to, is if they have retained the Pontiac balance, you could just pick up a new flywheel and install it. If they have zero balanced the engine, you would do grave damage to the engine by not having it zero balanced also.