Brake bleeding issues

The rear of the master cylinder is for the front brakes. Sounds like your brake push rod is to long and not letting the piston come back all the way. remove the brake light switch. The pedal will come farther back. If this works you will need a shorter brake rod or a spacer for the master. I had seen this already when someone used a e/b body pushrod.

You could also loosen the master nuts and let it push forward to create space for the longer rod for a test.