Is the master cylinder new? I had one go bad out of the box. Try opening all the bleeders and try gravity bleeding. Other than that re bench bleed the master and move on again.

56 Plaza 63 D100 step side 67 Coronet, 68 Roadrunner, 69 Super Bees, 69 Coronet 500 convertible, 70 Roadrunner Post, 79 D150 360, and a severe case of Mopar a,d,d