I have had 2 old squares with factory A/C and the stock A6 compressor. My current 83 looks like it still has the factory Frigidare compressor. Both were changed over to 134A and both had significantly less cooling ability after the conversion. Now that R12 can be had cheaply and is still plentiful, according to a local A/C shop, I would stick with the R12. I am not saying that 134A does not work, just saying that R12 was way better in my trucks. On 110 degree days in the desert the 134A is noticeably less cool than R12. On moderately hot days - say 90 degrees or less - the the difference is negligible. However, at 90 degrees in the desert it is time to roll down the windows and leave the A/C off - maybe turn on the heater
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