My '78 300d A/C has been out for some time now. My mec. says I need a new compresser and rec/dryer. He also wants to convert it from R12 to R134. I have asked around about this process and have had mixed answers. Some say no problems with the conversion, others say that the R134 puts more pressure (30psi) into the system and the molecules are smaller therefore leaks will happen. Has anyone converted to the newer R134 and what are your results? Any other comments??