cobbled brake system

Peddle going to the floor; manual, or power; no leaks dribbling fluid, is a bad master cylinder; change it out now before you loose brakes entirely: quick question: does the peddle pump up and hold?........."C" body disks up front is an inexpensive, maximum braking up grade, a little heavy, but cheaper than Wildwoods, parts are common in any auto parts store..........don't know about Jeep disks on an 8 3/4, would think that would have had to convert to "Green" axle bearings to eliminate movement of axles in and out, OR (it just struck me) MAYBE, housing wasn't converted to "Green" brgs and axial float is pushing puck back into caliper, causing excessive clearance, and is the reason you have so much peddle travel......the adjustable prop valve is not a bad idea, nor a bad thing in your braking system, if you are not experiencing rear wheel lock up during braking, it's doing it's job