No brake pedal

[Jblackie47803]

My '67 Long Fleet had been sitting at my parents' house for about 9 years when i decided to go get it and put it back on the road. The brakes would pump up good on it but would gradually fade and the pedal would drop the longer you sat stopped at a light. There was no fluid loss, so i chalked this up to a failing master cylinder. I got a new one, bench bled it and installed it. Tried to bleed the brakes but couldn't get any pedal back. Since then I have installed all new shoes, new wheel cylinders, new flex hoses, replaced most of the hard lines,replaced and adjusted the old frozen screw adjusters, and even went and got another new master cylinder and installed it. Still cannot get any pedal feel. Could the prop valve be bad and cause this. Every bleeder yields fluid and no bubbles when opened. Truck is all drum and no power booster.