I replaced all the O-rings in the system of my 300D, re-used the original compressor, a Delco R4 unit, replaced the dryer and recharged it with R-12 and it works well. The only problem is that the CCU is a bit flakey but it does manage to keep things nice and cold in the heat.
It's always a good idea to replace the dryer especially if a system has been apart or not working for a long time. They're fairly cheap. I paid less than $20 for mine.
Apart for the CCU, the manual system uses basically the same plumbing and hardware as the automatic system.

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DJ


84 300D Turbodiesel 190K with 4 speed manual sold in 03/2012