When I switched to alternator, I found a delco distributor, and made sure that there was a somewhat lengthy warranty period on the rebuilt I purchased (I think it was about 100 bucks because I didn't have a core). Unfortunately with these old cars there can be many issues with the electrical system.

I resoldered my fuseblock after the alternator upgrade (you need a very hot soldering iron to do this correctly) and that helped my issues a little. But apart from the alternator upgrade, the single biggest improvement was when I cleaned the ground spot where the negative batttery cable connects to the body. Now everything works great. My symptoms caused by the bad ground were maddening. The ignition switch appeared faulty, and the car registerd great voltage, I was very happy to figure out that it was the battery ground.