Well, my a/c problems are mitigated for the time being. I converted back to R-12. I had several cans lying around and nothing else that takes the stuff so what better use? Indy did the job, breaking the fittings and flushing with methanol and changing back to the proper oil. It seems one of my problems was the green dye that someone had added to the system. Indy stated that the dye is carried in oil and to properly add dye, a corresponding amount of oil needs to be removed. He estimated that there was way too much oil in the system. A simple evac and R-134 charge might have cured it but no matter.
What matters now is that I have to turn the system waaaay down (toward warmer) or I freeze out of the car. I had a 400 mi round trip on Saturday in 90+ heat with near 100 heat index and it was blowing 42 deg. air with no degradation in performance over the day. Engine temps are very slightly elevated around town but it stands to reason if more heat is removed from the cabin it's being introduced to the air stream ahead of the radiator and could result in higher temps there. Temps on highway were fine.
Thanks to all for the input. I'll keep tabs on the results long-term but for now I'm a happy boy.
Chuck.

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1983 M-B 240D-Gone too.
1976 M-B 300D-Departed.

"Good" is the worst enemy of "Great".