Thanks, Justin V.Grade 8 bolts are good. The factory rivets are just a tick smaller than 7/16". Grab a good drill bit and open up the existing holes where the rivets were and use 7/16" hardware and the locking nuts that are all metal. It'll be stronger than the rivets ever were.
Any idea the specs on that cross members' bolts and spacers? And a trusted location to purchase from?