Grand Cherokee Master Cylinder and Brake Booster Swap

I know this doesn't help whatsoever but when i did my swap (and anyone else reading this who is going to do this swap) I used a Wilwood proportioning valve WITH a brake fluid pressure switch for the brake light/cruise. Avoid the headache of making the factory switch work.

89mock, sounds like your on the right path to getting the lights working properly (and the cruise disengaging properly).