High Output Alternator Help

Hello,

I have a 1972 factory 318 AC Dart Swinger 2 door. It has an old alternator in it and my light are real dim at idle. Does anyone know of a high output alternator that I can install? It needs to have the ability to run 2 belts on it. One to the crank obviously and the other one goes to the AC compressor. Or is it possible to take the pully off the one I have and put it on another one.

Thanks!