E-tek,
Have you tried the 3M weld thru coating? It's for areas that you can't get to with paint after a panel is welded in. You can use it on both pieces and weld right thru it, works real good. The heat changes the properties into a very corrosion resitant coating. Not sure what, ain't no chemist but it does work well. It isn't cheap, comes in a spray can and can be had at your local auto paint supply house. Looks like you have your hands full with rust. My youngest son just changed cabs on his 67 due to rust. Living in the South we were able to find an almost perfect cab with just a small back corner area on each side needing replacement. Good luck with the project.
You bet! I use weld-thru primer on any areas actually welded (flanges, edges, etc.) and POR15 everywhere else.
Here's that tailgate with it's patches cut....welding will have to wait 'til after Xmas! A bit of surface rust on the patch metal was neutralized with Metal Ready (Phosphoric acid).
it is from the right time at least 42-47 
). Not to mention, these trucks are getting so old and so rare I kinda/sorta feel an obligation to keep them original to a degree. And before anyone mentions it: I bought my '46 with the late model running gear in it already or I'd probably have just upgraded the original 216 to a later but similar appearing full oil pressure 235; with dress up parts of course!
The Grille came out OK, but the front upper and lower valences where rust-welded together. I ended up cutting some off with the torch and some with the cut-off wheel. The bare rad support and inner fenders came off together.
