I went on a air conditioning course a couple months back as we are now doing it where we work. The answer to your question unfortunately is no. You can get adaptors for the high pressure and low pressure posts to convert to R134a type but the R12 refridgerant will attack the rubber hoses and seals inside the system and cause all sorts of leaks.

You could try that kit on ebay, might do the job, just sharing what i've learnt