1965 barracuda charging issue

It...........just...........sounds.........like.........bad luck of the draw on alternators, you might check

Above, the charge wire. The way I'd do this is get it working, and with the engine warm, battery normalized, check both with accessories off, and with heater, lights, whatever turned on

With engine running to simulate "medium cruise" RPM let's say 1500-2000RPM or so, check battery voltage should be normal at about 14V nominal

Now check the charge wire, if there is more than 1 volt difference, start looking

If the voltage is "way" up there let's say 17-18V then I'd really get busy.

Then take a good look at the brushes/ area/ slip rings for oil. Maybe you have a valve cover etc oiling the thing down some, etc.