360 balance ?s

A couple things you can try but I would bet it has to come out and apart to be corrected.
First try a different dampner and see if it cures it, if not you can try adding some weight to the convertor at the spot where the weight is now and see if it gets better, or you can even knock the weight off the convertor and see if it improves or gets worse, it can easily be welded back on. But in my experience it is uncorrectable without rebalancing the rotating assy if it is not as simple as a spun dampner.
We just went thru a scenario almost identicle to this in my shop and after trying to diagnose the problem, replacing the dampner, then by adding weight to the convertor we ended up having to remove the engine and check the balance and it was way off. After correcting the balance problem the vibration was gone.