Hy 56 stepside, did you bench bleed your rebuilt master cylinder before you installed it? You have to adjust your brake shoes up to proper clearance to achieve any pressure, otherwise the shoes have nothing to press against, and hence no pressure on the pedal. Incidently we don't want any air in the hydraulic brake system, that is what you are trying to remove in the bleeding process, air can be compressed, liquids cannot, so if you have air in your system it will compress before the brakes can apply, resulting in a spongy or no pressure pedal. You said everything was new, does that include your steel brake tubing and the three flex lines in the system?
