After installing dual electric fans, and having a 680 watt amp, I looked at my options on alt. After much research, and realizing that the weak spot in my truck, was at idle. So I ended up doing a smaller drive pulley for the alt. This makes the alt spin faster at idle. It solved all of my issues. AC on, headlights on, fans on, at night, and stereo cranked, I'm at 13 volts at idle. Before I was at 9 volts. So it all boils down to, your needs, and what your trying to accomplish. Fo me, the smaller drive pulley was the answer. I like
@jus10inbrla idea, and use our local pull a part a lot. There is 1 in my town, and I know there is at least 1 in his town. We are only about 50 miles apart.