I intend to use this car as a commuter and so AC is important. This will be my first attempt at conversion from a R-12 to a R-134A  based system. There's a lot of material on the web about this subject, your mileage may vary. 

As you might imagine the AC hoses look pretty bad. I have since removed the rubber portion but so far have been unable to find anyone willing to swage the new hose. Tens years ago this was easy job to have done. Now, nobody will touch them. If something doesn't turn up soon, I guess I'll fall back to plan B and use hose clamps (how cheesy). The previous owner tells me that the compressor does work but loses a charge in about 6 weeks. Buying a used compressor is an iffy proposition. I could, for instance, clean this one up and sell it as a good unit. The buyer would probably not know it was marginal for several weeks. This potential "junk sale" should drive the Ebay cost of a used compressors way down but some will pay the price AND take the risk. I think this is an area where I'll bite the bullet and go with a rebuilt (and warranted) unit. Late note: the failure rate on rebuilt compressors is very high also.

The condenser is also shot. I managed to ensure that when I was pulling the engine. Together with a new compressor, that will come in at around $500; so you can see this is a pretty serious part of the car for me. More on this as the parts come together.

Update: I bought a freshly rebuilt compressor from a law student over in Tennessee.  With shipping, I paid $175 and I feel like I got a fair price. I also ordered a new replacement condenser ($140) and refrigerant (R-134a). Will try to provide some photos of the hoops I had to jump through to service the AC.

For now I can tell you that my freon charge lasted only about a month before it leaked out. I had some dye in the system to help me know where there were leaks and one of those was the low pressure side Schrader valve. I still need to revisit that. Generally, the cooling air was marginal and the power needed to drive the compressor seemed to be more than I've noticed on other cars of equal engine size. I'm not quite ready to give up on 134 just yet though. I plan to swap out the expansion valve and filter/dryer and try it again. I also need to install the 134 fittings and to do that, I'l need to replace the compressor belt (40-5/8) with on that is a bit shorter (39-5/8).

R-134 suitable O-rings -  here are the o-ring sizes for my 85.5 944 NA:

                2 of 10.6x2mm
                2 of 7.5X2mm
                2 of 14.0x2mm