No A/C experience?

If it was converted to R-134A, the PAG oil will quickly absorb moisture from the air to form acids, which quickly corrode the innards, in even 6 months. If flushing, I suggest Hella PAO 68 oil, which doesn't absorb moisture, is more efficient, and compatible w/ all refrigerants. Can buy on ebay. I suggest HC refrigerant (Duracool or Envirosafe), but you can find many rants from gomers who know nothing about combustion yet state it is explosive. Millions of cars use it and no fire anywhere. I use in all my cars. R-134A is being outlawed and R-12 is very hard to get. The RV-2 compressor is dependable, but a heavy beast. You can find a post on the slant six forum giving options for newer compressors (mostly Sanden).