I'd have the alternator out and over to the auto parts for a test. You may have shorted diodes or just a bad regulator.
Understand this: if the voltage "output" of the alternator is not higher than the charged battery voltage (about 12.4), you are not charging at all - your battery is draining through the alternator, etc. Typically 13.8 VDC is an alternator's output voltage when the regulator is performing perfectly - and I say VDC (Voltage Direct Current) because a bad diode can add AC (Alternating Current). AC won't charge your battery, and over time can damage it.
At an alternator test station, they often show a picture of the output waveform, and bad diodes show as pulses of distorted or even reversed voltage (it's never too smooth, but a good one is repetitive, without differences)
50 years from now - how are we going to restore a "classic" microprocessor based modern car?? Alfas - 1980 Spider, 1987 Milano, 1976 Spider