From what I can tell, the brace is there to provide extra torsional stiffness to the body. Looking at that design, I'd have to vote "no".
IMHO, It would be an improvement over the spacers - which relegate the brace to doing nothing - but with bent edges like that, the ability to resist body twist is very low. Not zero ... but low. An improvement would be to weld in long, triangular gussets lined up with the diagonal lines that connect the holes in opposing corners
You would probably be better off leaving the brace off and installing connectors than installing either of these two solutions.
