[Modges'66]

I also sealed the seams in the box using a epoxy panel adhesive.
this adhesive has a longer working time than epoxy seam-sealer, and is widely used in place of welding on van sides (very strong stuff!). Prior to doing this I noticed that many of the original welds to the outer panel never took-hold, so I drilled the original weld locations thru the first thickness & inserted a self-tapping sheet-metal screw to pull the panels together, then drilled a hole next to it to plug-weld the panels back together, while advancing down the panel until the problem was corrected.
The results were excellent!
I also got to add a fist coat of primer.
Moving forward to block-sanding soon!