system is probalby fine. do you know anyone who works in the HVAC business? they can evacuate the old R12 freeon out for you then you can disassmble and replace the Orings at all the connections when you install in new truck. then you can refill it with R 134A, but all seals must be changed in order to change to the new freeon. Ithink there is still a kit available to convert that has a pressure regulator in it but have been told it is not really necessary if you change all the O-rings. Or you cna have the R12 put back in if it has not leaked out already.