Technically, A Pontiac is not an internal balanced engine from the factory. The front balancer is neutral, but the rear flexplate (flywheel) is not. Pontiac used the rear flexplate as part of the balancing. It is not a “neutral” flexplate, so if you are talking a stock engine, you need a flexplate designed for the std. Pontiac engine.
Problems arise while engines are rebuilt and balanced. It is more of how it is balanced. If the internals are neutral balanced, then you need a neutral balanced flexplate. If your engine guy used the flexplate to help balance the assembly, then you need to keep that flexplate with the engine.
You should not use a neutral balanced flexplate on an original engine, which is what I think he is trying to say.
