A handful of us in VA have been through this, and I think Doug Dolan has landed on the best alternative. He has an S38 engine in his car, but that shouldn't make a difference. I know he went to a Sanden compressor, and the largest parallel flow condensor his mechanic could squeeze into the car.
I kept R12 and don't want to redo mine right now, but Doug is getting much better cold air temperature readings from his vents. I bought my compressor and the custom bracket for the M30 engine from Ice Air --
http://iceautoair.com/index-1.html. You can find better pricing on the condensor, but I bought them together. The bracket made the install easy. Guy there was very good to deal with; he installed R12 fittings onto the compressor for me. I had a couple of custom hoses made up as well (I tried making my own re-using the stock fittings and did not get the fitting exactly right. It was pretty spectacular when it blew up); if you are going that route let me know and I will hunt for the vendor I used.
Doug shows up at a lot of events, but doesn't post here a lot. Try sending him a private message on the condensor. It was a Summit Racing or Jegs stock item, but the sizing is important. It made a big difference in his system.