Local auto shop sell'* kit'* to convert the system. I paid like $50 for the kit. I has no real gauges to check the system. You will have pay someone to get the r-12 In most area it illegal to just dump in air. Which the reason it usallay best to get done professional. I lucky(sort of) out my car the r-12 had all leaked out. Just for fyi the non lucky part is that my a/c compressor worked for month then I hard some ugly nosies from it(had the hood open at the time) that was it. If compressor is bad the can cost lot on my 92 it is $500 for new. I am going to go the junk yard and pick when up for $70. They siad they would give me 30 day warranty. I hope this helps.
2007 Dodge Caliber v4 5714 miles(cvt) tranny)
2002 Malibu 3100 117000 miles