Our local Volvo dealer just replaced the compressor on our '91 745 after the clutch shot itself and locked up. They said you can still get just the clutch, but it was $350, and a brand new compressor (with clutch) was $500, so we went that way. The whole system took 3 "cans" of R-12C at $49 a can. With labor, the job was a bit north of $1000 with a 1-year guarantee. Ouch, but you gotta have A/C in Arizona. I keep a thermometer in the car: in the summer it gets up to 150+ F inside the car when parked in the sun.

The car's A/C has always been a little anemic when the vehicle has been sitting in the heat, especially if you are stuck in traffic. Once you get going, it cools the whole cabin in about 5 minutes with the R-12 system. Tinted windows help.

The dealer had no problem getting the R-12, but that might be a local nuance particular to the desert.

Good Luck