The push rod adjustment has been to long,to short,and right on. Pads are not the issue,it won't even stop well at an idle. I believe the booster is bottomed before the master has enough travel. Could a drum booster have shorter travel than a disc booster? Come to think of it this is the 3rd car I've known of with this problem. The 3rd car was a 69 Hemi Charger Originally power drum brakes converted to disc. The booster was removed and converted back to manual disc. Problem solved. Removing the power brakes on this car is not an option.
Doug