The ones I put on Ben's truck are 2" x 3" x 1/4 wall. I used 2" x 2" x 1/4 bars back to the frame, and then 1/4" plate for the mounts. And yes..they are dang heavy. I've built several sets so far. ExplorerEB96, Doug, Ben, Parli22 and I all have 'em on our trucks.
Tex, if you can make it up from hicksville, I can build a set for ya. I just need to know ahead of time so I can order the steel. Takes about a day from raw chunks of steel to finished product installed. Worst part (as stated above) is driver's side. I usually end up dropping the gas tank to put 'em in.