I have bled the brake system on my '77 Crew Cab to the point where there is no air in the lines, yet still the pedal goes all the way to the floor. The pedal has no stiffness at all, yet the brakes all work. They work, but not until the pedal is right at the floor. The pedal acts like theres nothing (as if the lines were wide open) until 3/4 of the way to the floor. The truck originally had a Hydroboost, Dana 60 front, and 1-ton rear brakes. It no has a Dana 44 front, 3/4 ton 13" rear brakes, and a master cylinder and vacuum brake booster that as working out of another 4x4. I figure that the proportioning valve shouldn't be too far off with all the changes together... but could the master cylinder just be too small or bad?