So, after going to all that work on the underside, an opportunity came up for some low budget Sand Blasting and Priming.
After giving it some long thoughts, I figured that rather than attacking the underside again, i'd just have outer Body and Interior/Floors etc Sand Blasted. Besides, this allowed me to leave the suspension installed which made it rolling on and off of trailers much easier. Luckily, there were no huge surprises as far as holes appearing.
Back home again, and collecting the remaining sand in it for my portable blaster.