check the brake pipe routing and do a pressure bleed. Not a pump bleed. Pedal pump bleed on old master cylinders is very risky, let me tell you why.
The pistons never reach into the far end of the cylinder, which then corrodes off by old unchanged brake fluid. When you push the pedal down it will tear up the seals. Use a brick or wooden plank to limit movement if you dont have or cannot make a power bleeder.
In your case, start first by removing the cylinder, and bleeding it on the bench, then install it. check and adjust the projection of the bullet nose in the booster - its adjusted by the star nut in the cabin. Once you are done. Now proceed to bleed the brakes. Make sure the brake rubber pipes are NEW, not old scrap yard POS jenyan quality junk.