Most of the Pontiac stuff is internally balanced, so they'll except any flex plate. But you still have to send your flex plate. But if it gets damages a new can be balanced to match your old one, no need to have the whole motor rebalanced. Same goes for Hamonic balancer. I guess that's what your calling neutral balanced. Just make sure you get your balance card, so later any shop that does balancing can do it.
The things they hide, the way they spin things, the excuses that they make and the things they omit.