no rear brakes and hard pedal?

[70396CST10]

By hard pedal I mean when the brakes did work you would push down on the pedal and it was free, like powerbrakes should be, until about 2 inches from the floor board and then it gets hard.. And by hard I mean from my leg pressure pushing downward on the pedal.. Last Saturday when I started working on this again the pedal got soft while driving meaning it would go all the way to the floor with hardly any resistance and no brakes..

I was hoping to avoid this but I guess I will just start throwing parts at the truck until the brakes work.. I think that is stupid but what else is a man to do.. I mean, it could still be the MC, prop. valve, booster, wheel cylinders, calipers, and who knows what else.. I would think it is the prop. valve or MC but I get fluid out of both with no problem?

Thanks..

James..