TOM, TOm, Tom, sigh.....

R12 can be purchased for a mere $14 per pound these days. It will certainly work with the R12 lubricant. Is it really worth risking the health of your compressor to save the difference in whatever refrigerant you are thinking about and $14 per pound? Are you aware of the consequences of a failed compressor? When this happens it scatters debris all through the system and the ENTIRE system has to be THOROUGHLY flushed, o-rings and r/d replaced. Is it worth such risk?

Don't be penny wise and pound foolish.

Best of luck with whatever path you take,