I would'nt consider a rebuilt now that NEW denso compressors are avaliable again. If you need a rebuild kit- I have one. I pulled my low-mileage one off the car and one cylinder had a score in the cylinder wall, so I replaced it.
80F isn't a good test of the system. No real heat load. You have to put gauges on the car and watch closely. Temp probe is helpful. Eek- those early cars are 15cc compressors instead of 17 ccs. I consider my white 86' marginal with a perfect R12 system.

M