The one I made didn't turn out so good. It probably looks nice in the picture, but if you see it up close its pretty crude.
I made the two sides out of 1" square steel tubing. I also run 1" square tubing side to side above and below the drawers and mig welded the frame together. I bolted some drawer slides to the sides, and made some drawers out of sheet metal.
I don't have any blueprints for it. I measured the van and made the two sides to fit, then welded the cross pieces in. Then I just made some drawers that fit.
I'm waiting for a van with internal tool/parts storage boxes accessed from a door from the exterior instead of having to climb inside then crawl on hands and knees in the van.
The new trucks have a bed that is so tall it's hard to mount a sidebox and be able to reach what's in them without a step ladder. Manufactures don't know what a "work truck" is anymore- they focus on "style" and "looks" instead.
This is why I'm keeping my truck as long as possible.
Soon, when I decide it is time to semi-retire and stop installing complete systems, I'll go probably with a Ford transit and downsize.
I'll be adding two more large boxes this year- need more room.
The smaller boxes behind the big boxes contain capacitors, start kits, media filters, sprays etc.