Manual to power brakes on 1961 Apache

[tchevs]

Hoping to get some help from you guys. I don’t know how to navigate to find the information that I need. I have looked online but i really can’t find the information. My son and i are working on a 1961 Apache 40. We cleaned up a 1980 2wd frame. Mounted 73-87 front suspension from a c30 dually. Added a 2006 Silverado 3500 rear with disc brakes. Installed the cab forward from the c40 on it. Cut the bed from 12’ to 6 feet. Lowered the stance a little. Dropped an 04 LQ9 in it. Installed new brake calipers, brake lines, hoses, booster and master cylinder. I bleed the brakes, no air left but yet the pedal doesn’t firm up. I thought it was the master so I picked another at the local junk yard. Still the same. Questions I have are is if the master we used does not push enough volume to those big calipers? Is there a chance that the pedal ratio doesn’t let the piston push in enough in the master?