[dsraven]

before cutting out too many panels think about trussing up the body, with the doors on and closed to fit resonable well, then weld in some bracing in a triangulated pattern so the cab can't flex out of shape. then the doors can come off and the panels can be removed/replaced. if there are lots of structure to be replaced sometimes the doors don't fit great after because the structure of the cab flexed when it was stripped down, or it was tweaked at some point in it's life, and then you fight with the doors after the fact for alignment and fitment. better to brace, tack in the new panels, test fit the door, then weld after the door has been fit. don't ask me how i know this.....

there are a couple of different kinds of weld thru primer. some is zinc based and works but spatters way more, some is copper based and costs way more but welds better.

I would recomend a sandblast of the rusty areas, if possible, followed by epoxy primer. sandblasted by someone who has blasted autobody before. remember that sandblasting can cause the panels to warp if done wrong.it will also reveal thin areas you may not know about till after. not a bad thing because at least then you know what you have right away, not after a year when the rust comes through the thin spots. the epoxy can be sanded off to expose clean metal before welding in the areas you will be repairing. weld thru primercan be used before welding on the newly exposed metal, then weld and after finished the weld thru can be buffed off the externally showing spots and a new coat of epoxy sprayed on. epoxy sticks way better than weld thru and seals the metal better. weld thru will eventually have rust appear. spray epoxy liberally over the weld areas, seal with a bead of autobody seam sealer, topcoat and hope for the best.