Ignition Upgrade

Yup. And the disc is limited to stopping the advance, which is the opposite of what needs to be done in many cases.
I really don't understand what you mean by this statement the disc shortens the amount of mechanical advance. If you want 34* total and 20 initial you simply use the 14* slot, it's a mechanical advance limiter no different than welding the slots and filing until you get the initial and total where you want it or loosening the 2 screws on a Real MP distributor and shortening or lengthening the slot to control the travel... what are you trying to accomplish?