the flywheel itself comes balanced. However, I have never seen a balance weight attached from the factory. They normally accomplish balancing the flywheel by drilling the flywheel itself. If there was a weight attached to it ,my guess it was put there when a dynamic prop balance was done at some point in the past. In which case you would need to redo that, to attain the same level of balance you had previously. FYI, if the engine was overhauled that weight should have been removed from the flywheel assembly anyway, had you not lost it, as the engine and prop combination would now be different than it was before the overhaul and thus the dynamic prop balance would need to be redone due to the new reciprocating parts in the engine and prop combination.
Good Luck,
Mahlon