Lol there are much smarter people here than me.
It’s an amount of weight and a distance relative to centerline required to balance. Imagine one pound of weight, one inch from center. Then imagine one ounce 100 feet from center. The concept is relatively easy to understand. But this has all been figured out for you. B&M used to make two cutout flexplates, one for mag and one for LA if I remember correctly. Not sure if they still do. But it will be all the same stuff used to put a 904 behind a 360mag. Use the mag harmonic balancer, the stock mag flexplate, elongate one of the holes with a die grinder so it bolts to the neutral balance converter and you should be golden. Assuming your rebuilt mag was externally balanced as it was stock.
