If you want to be original, you can find the York compressor which was widely used in many 244s, as well as many older American cars. Should not be a problem to find them. Durable units, but unfortunately power sapping. Might be OK for the 164. On my 144, I retrofited a Sanden rotary unit with a custom made bracket. Lighter on the motor, as well as more efficient. Only problem I had was in stop and go traffic, it was not as cold as the York. Fixed that problem by installing an electric fan in front of the condensor. Works well. By the way, I am still using the R-12. About switching to R-134, there are retrofit kits out there, not sure if they work really well with the old condensor and evaporator.
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...and the bricks keep on rolling