Between the frame rails underneath the cab. Trucks are different from cars (unibody design, like a shell) in that they are body-on-frame. It looks like a giant ladder and they are generally 6-8" tall or more for HD trucks. You would create your own "skateboard" if you will then lower the original cab back down on top.
That does appear to be where Ford tucked the batteries for this one, this not-so-great video[1] does slide under and show them briefly. Not sure how it has two motors though, I thought the whole point of crate motors was as a drop in replacement for the existing engine (plus of course then they'd cost $7,800, before the batteries).
Sorry, I meant "seems like not such a great advertisement for DIY conversions if it completely changes the way the drivetrain works (and costs twice as much as the price of one crate motor, never mind the battery etc.)".
I grew up working on cars. It's really not that hard, especially with electric vehicles/retrofitting. The cab is attached to the frame with like 6 bolts. This is a very common practice in shops working on trucks - sometimes it is easiest to just lift the entire cab to work on the truck.
Doing restomod work is a lot of fun if you are into that sort of thing. You get to play 'car designer' and rebuild a totally new vehicle/powertrain while trying to make it look original.
Heard that modern truck engine compartments are getting so cramped you gotta lift the cab to even change all the spark plugs. This way dealers can charge $500-$800 for a plug change. (And diesels, which don't have plugs, have even more stuff ($$$) crammed in instead.) It's getting to the point where having the know-how plus equipment to lift a cab is becoming outright essential if you don't want to pay thousands for routine maintenance.
This is work, for sure, but honestly, it's one of the easiest chassis fabrications that someone can undertake. It's a box that sits between frame rails. You'll have to make considerations for chassis flex and ensuring it can handle the weight, but those are relatively easy.
And like moving a mountain, you do it one step at a time. I've done body lifts -- remove truck body, insert spacers, replace truck body -- with just a jack and a couple of 2x4's. Not hard, just takes time and patience.
And a niche that will definitely see players working to fill, if the last 100 years or so of aftermarket & tuner culture teaches us anything.
The first things I did when I bought a BMW convertible about 10 years ago was order BMW specific aftermarket wheels from a company that only sells wheels for BMWs. I also ordered aftermarket electronics from two companies that only market to BMW enthusiasts.
There will definitely be companies coming out with bolt-on battery packs for things like Jeep Wranglers and old trucks like this F-100. If bolt-on isn't possible, then it will be kits that the engineering has already been done and you just need to measure and weld on the mounts and then bolt on the battery pack and run the wiring.
My maths has it at approx 10,000 cubic inches of battery weighing in at 450kg, which rought and dirty is a 43 gallon tank (I may be way out) which is around 120kg of petrol.
Looks like standard is around 26 gallons (up to 36) so not miles away on volume, call it 1.5x. Wight and how you distribute it are going to be the real issue here at 3.75x the density.
