The York compressor soaks up a little extra power, but they are cheap and work quite well with R12. They don't convert well to 134 though. They just don't handle the added head pressure for very long.

For retrofit systems, the Sanden is the de facto standard. A variety of brackets are available and they are a very good compressor. Also, they are made in the USA. I've been in the plant in Sachse, Texas.