[lust4speed]

Moot point on the external balance since you mention that the engine will be zero balanced - which is good, but that means that the flywheel also needs to be zero balanced. So forget about any flywheel advertised with external balance.

All Pontiac V8's from the factory were external balanced with a six inch-ounce variance in the flywheel or flexplate. A stock engine can use any flywheel meeting the Pontiac spec as externally balanced. Once you have the machine shop neutral balance the engine then the external flywheel option is off the shelf and the neutral balance flywheel must be used. While I have machine shops change the balance of flywheels, at the current labor cost it is usually better to go with a new flywheel. By the time the flywheel is resurfaced and neutral balanced you are adding up costs pretty quickly.