I have a '77 450slc with a relatively new R-12 A/C compressor. System works but here is S. Texas it is battling to keep up. Although I can get the system charged with R-12 in Mexico it is a bit of a trip that I would rather not make. Can I (as some have told me) just charge the system with R-134? Some say the pressures required for R-134 will damage the comp. after a while. If I change the comp. to an R-134 what else should I change? Dryer? Expansion valve? Tks. for the info.