This looks like a relly cool project. Back when I had my 98 S10 I always dreamed of converting it over to a pure EV or even possibly a series hybrid. And when the engine died on me it seemed like the perfect oportunity... then it just took up space in my garage for almost an entire year while life carried on and I didn't have anywhere else to store it and I didn't even have the money to repair the engine so I just had to let it go.
Someday I would still love to do a pure Electric S10 but until then I will satiate my self by watching awesome builds like this.
Also not to put down your huge foam tonneau cover, but how much are you spending on that in material cost? I know you got the foam boards for free, but I only ask because over the years that I had my 98 S10 I was able to pickup 2 different hard tonneau covers for under $100 each. I even still actually have the flush mount one, I just cut it down so it would fit on my 88 S10. Also I'm pretty sure you have figured it out by now but the S10 beds taper from front to back by like an inch and a half.
Also I don't know if this will help any but here is a very detailed breakdown of an S10's design. It gives very detailed measurements and such of the body, frame rails and componant layout in these trucks.
http://www.gmupfitter.com/publicat/p..._Truck_pgs.pdf