brake pedal very hard,changed booster and master cylinder,and adjusted rod a few times,what now?

Check for vaccum to booster

After checking the vaccum, and if you have not already, you should start checking further down the line. A hard pedal is a symptom of air in the lines (air won't compress), bad proportioning valve, stuck cylinder(s), crimped lines and frozen shoes. Good luck in your search for the problem.

Actually, it is the opposite. Air does compress, fluid does not. Air in the lines will let the peddle go to the floor. That is why we bleed brakes, to get air out. As you bleed em, less air in the system, the peddle gets higher and harder.

Sounds like low or no vaccum at the booster. Hows the check valve that plugs into the booster? Air in the lines is a soft pedal.

Is the Master cyl leaking into the booster?Any fluid on the master cyl side of the booster wil tell you real quick.No fluid check the booster pull the vac line shoot the diaphram with some WD40 put the master back brakes, BAD booster 4 PIA bolts to get out