when I had cars with magnum 500 wheels I made my own adaptor to properly balance them.

I picked up a 70's 2 piece rotor and removed the rotor from the hub, removed the inner bearing races and installed new wheel studs. it slid right on the balancer shaft and I used a small cone to center the hub on the shaft. it worked perfect.
the only problem is I gave it to the buyer of the car when I sold it.