Voltage Regulator and low output from Alternator

Ok, with what you've done, sounds like the field is OK. If you can post a good photo. Inspect the brushes carefully, best to pull them out. You are looking for anything that could cause an unwanted ground (short) from one brush to the case

IF you can confirm that this is not likely, next put it back on the car and do a simple test

If you are going to continue to use the 69/ earlier regulator, ground one field terminal. Clip the remaining field to a battery source such as the starter relay big stud

Start engine, bring up RPM and see if it charges. If not check voltage at alternator output stud and see where it sits at "a good fast idle."