You could always put a 1/4" steel plate on inside of the frame to brace it. This would/should eliminate the frame squishing/squeezing problems.
Also, a question for the welders among us. If the sliderz were welded on, couldn't the welds be ground off to remove them. With a little more welding and some cleanup work, I don't see why the frame could not be put back to original shape. At the very least, a potential buyer of the truck would have to look very hard to see where the sliderz were welded on.:frog: