Hit the junkyard for body parts, because there's a million F-Series out there and if it looks the same it fits
(note door shape)
If you were to do only one thing to improve this process it would be to replace the dryer, and to add more oil. You can usually get dryers for thirty to fifty bucks for almost any vehicle.in the past with other vechicles Ive had I just vaced out the R12 then added R134 and never had a problem I know thats not the right way to do it but I know it does work so long as all the old refridgerant is removed.