OK Roadtime, here's the way that I did my vans. I bought a 10' x 5' x 1/2" baltic birch plywood from a specialty hardwood store in MO. On the sides, I cut out the wheel well profile and some minor cutting in the rear corners to accommodate that area so that I could drop the sheet onto the floor. No fasteners needed! I added a piece of steel 1/2" angle iron to the rear end of the plywood to protect from towmotor forks. Next, I cut 3/4" 'AC' plywood lengthwise into three 16 inch wide lengths until I had two 8' lengths and three 4 foot lengths. I made a cardboard template of the inner wheel well side and traced the outline onto the appropriate location of each of the 8' sections on the 'C' side. I used a router to remove a 1/2 inch of the wood within the outline. These plywood pieces will be 16" tall walls, so picture a 3 sided box, open at the rear. I made a 12' long box but the longer vans can adjust accordingly.
Layout one 8' and one 4' plywood end to end and fasten a 10' section of e-track to the long top ends of the 'A' side with 3/4" pan head screws. repeat on the bottom; the OCD part of me put a screw in every e-track screw hole. (A few will be removed later) I bought about 4 lengths of slotted angle iron and cut one into several 3" to 4 " pieces. These will be used to fasten this box wall to the floor. Place a piece of masking tape down the center of the floor and with a marker, draw a line down the centerline of the cargo area. Place one piece in position to mark securement points on the wall and floor. Measure from the centerline to the wall when pressed against the wheel well. This will be a bit over 2' and should be the same distance all along the wall. Remove a pan head screw and replace with a machine screw, washer and nut to fasten the slotted angle iron to the wall. Do this in about 4 - 5 places ensuring the distance is the same so the two long walls will be paralell. I drilled holes in the floor at each angle iron and placed a barbed T-nut from the floor underside. A machine screw fastens the wall securely to the floor.
I secured the wall ends to the rear door frame, used the 48+ inch wall distance between wheel wells to determine the length of the 16" xy 48+ inch piece. This piece need not be secured to the floor, just the wall ends. After installing the entire wall to the floor, we need to secure the top. I fastened a full length of slotted angle iron to the van verticle frames and secured the wall top to it, here and there. I cut 1/2" plywood to fit as a seat on the wall so that I had hidden storage for tools and securement equipment and other stuff. No all you need is e-track sockets into which you drop 2 x 4s. Eight sockets and four pieces of 2x4 will give you upper and lower securement for and aft of any cargo. Some DOT (not Wal-mart) approved ratchet straps and the load bars will secure most anything.
