I've had a whole plethora of stock 40s and 50s GM vehicles over the years and experienced all kinds of different anomalies and failures related to generator/regulator systems. I also learned that when it comes to these systems, do NOT tax them by running them at near to or max capacity. Also, always make sure to properly polarize the regulator and generator, and ALWAYS make sure to change the condenser of it's more than a few years old. So many minor things can be done to see that these systems last, but it's often the experience and knowledge that is lacking.
Biggest problem I've found is pitted regulator points caused by not polarizing the generator, running a bad condensor, or a dirty commutator. Also, the generator and regulator have somewhat of a 'symbiotic' relationship with one another... that is, if one fails, it often taxes the other and it fails shortly thereafter.
The original Delco-Remy regulators are very serviceable, and if you have one, best to keep it in service if you can. The new reproduction ones are pretty lame, so don't bother with them.
And don't run A/C with a stock generator. Just don't do it!
