You need a disc brake pedal which is longer than the drum version. OEM manual transmission ones are hard to find, an automatic pedal can be modified. You already have a template of the metal portion for the rubber pad.
The drum brake pedal assembly hanger can be modified for use with vacuum boosters. You will need to remove 3 of the nutserts where it mounts to the firewall.
Scott Drake offers a reproduction manual transmission disc brake pedal, that will work, but it is a copy of the 1969 pedal. It will not have the pedal return tab.