Zippy, I took 2x3 but also opened the front of the rear frame rails and stuffed the 2x3 about 12inches into them. But first you take a hole saw and cut holes on the inside and outside of the frame rails. You want to stagger them. you have to take clamps and pull the frame rail against the tubing but then you can also weld the frame rail connectors to the sides of the rear frame rails. Very stout setup. But you have to bring the 2x3 through the floor pan at some point. You then have a place to weld the main hoop kickers on to. have fun matt s