You know, if your xj was a show car touring the circuit of mall parking lots and convention centers, then treadbrite would be a nice interior visual. On the other hand, hauling things in the rear would become a skating rink without great tiedowns everywhere and the noise would be incredibly amplified from the rear end. That is what the carpet and pad helped eleviate. Another idea ,as stated above, would be to cut out the cancerous rust and patch with galvanized flat pieces using rivets and a good appropriate adhesive. Then crawl underneath and undercoat everything in sight with your choice of coatings or several coats of a good epoxy paint. You gotta address water issues. Then for interior cover and soundproofing, cut to fit a rubber pad like those great truck bedliners you see around. Maybe it's not the bling bling your wanting but it would definitely cut down on the blang blang from beneath. You could always put some treadbrite on the quarter panels. Good luck.
