Brake pedal will not come back up

[mntoy]

Still having problems with the brakes on my 1974 Chevy C20 2wd truck. I have already replaced the booster and MC from Azone, benched bleed and installed. Took forever to bleed brakes and finally finished then drove the truck for 3 or 4 days about 80 miles with no problems. Get into the truck today pull out of the driveway and at the first stop sign I step on the brakes the truck stops makes a horn/whistle type noise and the brake pedal is stuck to the floor and the truck will not move (brakes stuck on) and the brake light was not on. Had to turn the truck off and push the pedal a couple times to make the pedal come back up. Started truck and put it in reverse and drove back home. Yes it happened a couple more times on the reverse trip home. One other strange thing is the MC cover leaks over the back reservoir only. The trouble shooting instructions for the Azone brake parts say the pedal push rod is to long and to shim between the MC and booster to shorten. Installed a set of body shims and still have the problem. Not sure what to think, can anyone help? Mike