You must not be too far south or your ambients would be higher than what you reported
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The best thing you could do for the car would be to open everything up, flush, button everything up with the proper oil fill, vacuum and charge with r12 like the car was designed to operate on.
Another option, and I have never looked into this, would be to install a 1995 E320/300 condenser in the earlier car and try it with 134. Not sure if the expansion valves are different between the two.