Shake rattle and roll

Went through the same mess that you are experiencing with a stock Magnum serpentine set up on my Dart.
Bought three H. balancers before I got the one with multiple weights that actually worked. Do not remember which one was correct.
However, since it was made in China (GAG) the crank hole was TOO SMALL. What! It would not fit on the crank. Had to have a machine shop bore it to fit.
So, keep on fighting. And, assume that if it is made by anyone except Mopar to measure everything.
A friend back East had one that the keyway was off compared to stock.
"It is always Something"( Rose Ann Roseanna Danna )