Caleb is correct. OD is still 3.5 but 1/2" thick. Dually ones are wider but you can narrow them it you like. Can't tell you the thickness on the cab and chassis tube. I would personally stay away from the dodge 11.5 read ends. If you ever decide to put big axles in them they tend to require machining the tube out. GM ones don't. You should be able to truss one up enough to last.