[hgs_notes]

Might be a dumb question, but is there good vacuum to the booster? You really won't get "good" pressure to the calipers during bleeding. But wuth the truck running and good vacuum to the booster, the pedal travel is not really very far. The rod from the pedal to the booster may have been swapped with the one for the master cylinder you replaced, in which case, it might not work with the "correct year 1972" booster/master cylinder. If it was mine, I would check for good vacuum to the booster, then if that was ok, I would run to the junkyard, find a 67-72 truck with power brakes and get the rod from the pedal to booster and compare them. If it is different from what you have, that may be the problem. Another thing, sometimes the flexible brake lines to the calipers weaken and will flex with applied brake pressure, reducing the amount of fluid pressure to the calipers. All it takes is one week line and the front brakes are spongy. If not, keep bleeding the brakes.

BTW, I never bench bled my new master cylinder when I made the swap, and had no problems. I had also replaced all the lines for the front brakes at the time.