383 Harmonic balancer question

Correct, typically the inertia ring is drilled to balance the damper assembly in production. Drilling the balance holes at a larger radius gives you more balance correction. As GTX John stated, those balance holes may have been drilled in the damper hub to balance the rotating assembly, has merit here. 65'
I agree, they are remarkably different. But the OP says he has a bad vibration. I don't believe the small amount of metal removed from that neutral balancer is enough to cause a bad vibration. I could be wrong. It's happened a lot. lol
I tend to agree. This thing rattles my fillings out. I’m just not sure what else it could be.