I was gonna do it at one time & I checked into it somewhat & they said: convert to the "barrier"? hoses, replace the reciever/drier, replace the valve that sets just forward of the firewall there on one of the two lines that come out from it, do something (change?) the oil in the compressor and maybe some more things. Heat dont bother me so I let it slide & I've been in some R12 cars & its like being locked in a cooler