Can anyone offer me some tips on welding a vehicle frame together? What I would like to do is cut a vehicle frame in half(because the rear frame is bent) and weld a good rear half back on to it. The truck frame would need to be cut in the center, so there would be a lot of stress in this area. Please be aware this frame is a box type frame.

My plan is to make a top to bottom vertical cut and then weld it back together like a butt joint. What could I do to make this area as strong as it needs to be.