Mike, Patrick's sells a reasonable kit for $80 that uses the single belt off the balancer, but uses the double pulley off of the compressor to allow for a dual belt installation.
I made my own brackets (stock '57 3600 235) when I installed AC about three years ago. I wanted the compressor on the top and the alternator on the bottom and all the kits that I saw (including Patrick's) were the other way around. Not too hard to do, but it did take a fair amount of time to mock up and fine tune. I enjoy the challenges of that kind of work, so it was a pleasant project for me. Mine uses a single belt. If you are interested in doing something similar, I'd be happy to provide pix and info.
Matt
