Converting is fairly easy. First, I advise changing the OEM piston compressor to a rotary type. We often use Sankyo compressors from an old Toyota, Nissen etc. They bolt into the stock bracket with a simple adapter (also available from Sankyo) This saves having to drain & clean the stock compressor sump (its less efficient anyway). All your stock lines will bolt right onto the new rotary compressor, the electric wire for the magnetic clutch plugs in and the same vee belt will fit. Next, replace the expansion valve under the dash with an identical one set for R-134a (slightly higher flow). Be sure the wire cloth filter in one leg is clear (if its there; some shops leave it out for even higher flow). Replace the dryer assembly. Finally, suck on the system for at least 1/2 hr with a vacuum pump to remove all moisture and the remnants of R-12 compressor oils. This is the minimum; replacing all the hoses with new barrier o-ring-type hoses will reduce leakage with the smaller R-134a molecule. Good luck.
