Vintage air in a 69 Dart

also if your looking to convert to R-134 (which is recommended for price of freon) you need to change the dryer, condensor coil, and lines... im pretty sure you can flush the Evap coil...

also change the ALL o-rings to the green ones...

I never have had to do that I just filled the system when it was low on R12 with R134 and it works fine and freezes you out.