[tucsonjwt]

I am no A/C expert, but your first decision is whether or not to keep it R12 or change it to 134A refrigerant (assuming that it has not already been changed over to 134A.) Around here, you can still get R12, so I would go that way if it is still R12 - otherwise, you will/should add a "pusher fan" in front of the condensor and change the condensor to a "cross-flow" condensor.

I would first take the truck to a mechanic have an "A/C special", where they can pressure test the system and tell you what kind of refrigerant you have, then give you an estimate of what you need. Once you know what you need, you can shop for those parts online and try to find a mechanic who will install the parts and fix your A/C for labor cost only.

I would post back here once you have a list of what you need and get some expert advice.