I'm using a 150A stinger GM style big case alternator. Works perfectly with the March Perf serpentine kit. The only think I had to do differently is the adjuster bar for the alt - I had to move the mounting point to one of the timing chain cover bolts. The spacer is pretty close to the harmonic balancer (around 5mm clearance at the top), but that hasn't been a problem so far.

I've got an MS, A/C, 1400W (RMS) stereo, alarm, aftermarket lights (soon to be HID), 4 (ran 5 for a while) electric fans (2 for a/c condenser, 2 for radiator) etc.etc. and I can idle with everything on @ 800rpms at 14.5v.

Here's some pics of the alternator, brackets, pulleys, etc...
http://www.cardomain.com/ride/2324498/4
Unfortunately, the changed rod mounting point isn't really visible in the pics... I'd take a pic of the changed bracket, but everything's all apart right now for a rebuild.