Boxing a frame is probably the most common thing done with a old frame to ensure it holds up to the stresses applied to it by upgrading motors, suspensions, and running gear in general. The "hotrod" and "streetrod" mags are full of this kind of information. If your truck is exploded to the point where it's nothing but material and time to make it happen then I would go for it. It sure can't hurt. Check out the old mags on this kind of project as they give many helpful insights into the little tricks like welding in nuts and mounting plates to make reassembly easier. Good luck.

Six volt guy living in a twelve volt world