Having installed some AC systems in older cars for which no AC kits were availible, I have some questions and suggestions. First, does anyone make a Sanden replacement compressor kit for the Delco R4 compressor?
I've seen kits for the older Fintails and W108s with the York, but nothing for the R4. Second, if you're going to convert to R134, the parallel condenser is a great idea in theory. but the condenser and lines need to be custom made or fitted to work in a W123. It's not a simple bolt-on upgrade, and not neccessary if you can run R12.

As for the rough & noisy Yorks, it may not be neccessary to spin them as fast as they do in our Benzes. I had a customer many years ago with a Sears hang-on AC in a '67 Mustang, and a bad clutch on his York compressr. e also commented that his car always ran hot with the AC on.
So I 'de-rated' his AC by installing a replacement clutch with a larger pulley to drive the York about 20% slower, for a reduction in load on the engine and cooling system.
AC cooling was also a bit reduced but still acceptable.

Around this time I adapted a Sears hang-on AC for a friends 1976 4-cylinder Mazda Miser wagon. The Mazda already had a vacant factory pulley mounted on the crankshaft, but it was sized for the Sankyo (Sanden) compressor that would have been installed by a Mazda dealer. It probably was driving the Sears-York at least 30% slower than normal. AC performance was a bit weak at stoplights, but otherwise it cooled OK, and the load on the 4-cylinder engine and cooling system was barely noticeable.

Of course both these York-driven ACs were using R12.

Happy Motoring, Mark

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DrDKW