The biggest condenser fan would be the best. WHatever moves the most air across the condenser will make the best impact on heat transfer.

Regarding the condenser, the R134 condenser is more expensive, but transfers heat better. It will make a difference.

Third, you don't have an accumulator on a 1990 240. You do have a receiver-dryer, that should be replaced if you open the system up. It's cheap; replace it.

Overall, the properties of R12 refrigerant are much better suited to automotive air conditioning, in the commonly found ambient temperatures. The pressures are more even and don't vary as much in different ambient temperatures. That makes the requirement for other things (different condenser for example) less important. The R12 system should cool pretty well in all climates, as long as the compressor is compressing properly and the condenser is intact and cooling fins are clear.

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Chris Herbst
1992 745, 68k

And others:
93 944, 150k
90 245, 110k
88 744, 160k
87 245, 185k