93 Ford Explorer A/C

I have the same problem with my 1993 explorer however, I've done some research which shows that prior to 1994 all systems were using R-12 unless it has been changed. Since the R-12 is so expensive and I dont know where its leaking I think I'll change over to R-134. However, Im going to follow the right procedure by flushing the system and removing the R-12 oil from the compressor and replacing it and the rings with the compatible parts I dont want to mess up my compressor they're expensive