Old Regulator Internals
The electro-mechanical ones have some combination of relays and primitive electronic components. In use, it seems to regulate to a maximum of 25 or 30 amperes as the primary regulation mode depending on the model. This picture is what (a fried) one of these looks like inside. It seems an appropriate device for a 40 year old car. Fragile, a new one may not work the first time and has a habit of taking out the generator when something goes wrong - or a problem with the generator will wipe out the regulator. My car has gone through 3 VR and 2 generators. The first was lost when I hooked it the bad generator in an attempt to save money by replacing the cheapest one first. No money was saved.