New battery. New alternator. New regulator. Rebuilt carbs. Starts up and runs like a scalded dog. The only problem now is the generator light comes on if the revs dip below 2500 rpms. I don't mean dimly glowing but fully on. WTF! I am happy she is running well but I feel a little wounded after paying all this attention to her (her name is Ilsa) that she would treat me this way. Any thoughts? Gratuitous picture of heat exchangers included for no apparent reason.

congratso!
before i launched into the alternator I would try a new voltage regulator. I got two bad rebuilt bosch units before the present one. First one put out 15 or more volts and second wouldn't provide a response at all below 2000 rpm. It a little bit easier to swap that VR and a little cheaper too (although my parts guy did take one alt back after I had it for a week- he gave me the vr and said come back and pay if it fixed the problem).