r134a or freon

R-134A lines have a nylon barrier layer where as R-12 lines do not. R-134A molecules are smaller than R-12 because of the lack of the Chlorine atoms. Even if you convert over to R134A you will still need an orifice tube or the better choice would be the expansion valve. If you use an orifice you must have an accumulator instead of a receiver dryer.