I got a 150A alternator from these guys:
http://www.mralternator.com/main.shtml
I retained the factory wiring, but added an aux wiring kit from Summit. I believe it was a 2 or 4 gauge wire with inline fuse. This heavy gauge wire runs from the alt to the positive battery post. You can take a look at it on the next run we do if you like, although I ma sure you'd like to get this figured out sooner.
The Summit part number was SUM-890025-1 and their description "ALT WIRE KIT 80-150 AMP". I can no longer find it on their website, but if you call they might be able to help you out. It was $19.95 on 12/05.
You of course can get a heavy gauge wire from NAPA or local welding supply by the foot. You'll have to figure out your inline fuse holder on your own if you go that way.