Upon doing some research, I discovered that this is particular issue is somewhat common when trying to pair a South Bend disk with a ACT pressure plate. It's partially due to the thickness of South Bend disks and partially to ACT design changes. Basically it's hit or miss whether they'll work together.
If you have some links, I would love to take them for a read. Particularly over the ACT design changes. I tried digging up info direct to this combination and all I find is "+1 act 2600/southbend combo" posts with no substance about engagement point, preloading, etc...
Is it the newer PPs that are a problem or older PPs?
I think I now know the real reason the person was selling it...
