Okay, here is the way I set up my Ford van, after several tips from everyone on here.
FLOOR- I welded 2-8 ft sections of e-track to the floor, spaced evenly apart,(24 inches) then screwed 3/4 inch regular plywood to the metal floor.Stained and polyurethaned.
WALLS- There is 12 inches high on each side against the wheel wells from front to back of 1/8 thick steel, welded to 2" high angle iron, which is welded to the floor.There are also one row of e-track welded to the side walls.
FRONT WALL- The 12" steel continues and connects the 12" side pieces together in the front and welded together, creating a 12" high steel box with an opening in the back, at the rear doors.The rear airtight wall/bulkhead of the sleeper is bolted to this front 12" high steel and bolted to a 2" piece of angle iron at the top, going from side to side, welded at both ends.The back wall is 3/4"plywood also.
I prefer straps, ratcheting.But I do have those brackets that hold 2x4 pieces into them that snap into e-track also.If you want to use load bars,Find some at docks and ask if you can have them, and drill out one rivet using a 1/2" drill bit, and then pull the end out and cut the rectangular body 5" shorter than you need, then slide the end back into the body and drill a new 1/2" hole, and use a 1/2" dia bolt and stop-nut.
Keep in mind, this added alot of weight to the van, so you may want to use lighter materials.I wanted some kind of protection between me and the freight.(straight truck driver thinking)