I've been following the bent truck frame but can't really contribute much beyond the basics I already suggested. FWIW when I saw your question, my first thought as to where you'd find that info was "a collision repair shop." It's extremely specialized information that's undoubtedly going to vary between manufacturers of frame repair rigs.
The one thing I thought I'd drop in here is that I watch a couple Youtube channels who are world-class experts in frame repair - one of which is Salvage Rebuilds UK - and I've never heard them mention manuals or spec sheets. They use the methods that have already been suggested, which are careful measurement, triangulation around points of symmetry, etc. You start with what you know is good and makes sense and work from there.
I think you're going to have to pick a collision place you trust and just accept their opinion, then make plans for how you want to approach it. Anyone who's been at that gig for a while is going to be able to give you really useful feedback just by eyeballing it. Once you have 2 experts saying the same thing, it's time to look at what else might be going on. Wish I could offer more than that, but if it were me I'd be under the truck with a tape measure and a piece of string and a plumb bob and taking lots of measurements.