http://autorefrigerants.com/co00033.htm
no need to convert anything, did it to my DA years ago. But since removed the a/c system.
Quick-kit with R12 tap/chargehose and Dyecharge/Refrig. combo (instead of 134a tap/chargehose and conversion fittings): Order here $39.95 ($4.00 shipping). ( comes with 3 cans of ES-12a dyecharge product and a custom R12 tap/chargehose for installing dyecharge directly into existing R-12 service fittings). R12 chargehose fits oil-charge, stopleak and all other Enviro products.