replaced EVERYTHING and still have no brake pedal

I am out of parts to throw at my brakes. Not that it should effect anything but I have 3/4 ton chevy brakes upfront and 3/4 ton ford brakes in the rear bth front calipers are new as are the rear weel cylindars. I just put a new master cylinder in it today. Yes the master was bench bled. I bled about a half gallon of brake fluid through the system with a power bleeder. I tried pumping between bleedings. I replaced the load sensing proportioning valve with a T. My rear brakes are over tightened, so I know that is not the problem. My lines sat disconnected for about a year and a half. Could the return line from the rear having air in it be my problem?

Did away with the return line and brakes work great

what did you use to cap every thing off?

What master cyl are you using to push brakes that big?