PO replaced complete rear tub including wheel wheels with heavy steel, for some reason they notched here, both sides I think it was because if left it would show on the outside skin of th truck, they should have only notched smaller section.. weird I know. tub and wheel wheels are checker plate from behind front seat brackets all the way back..
previous pic shows the one area of minor surface rust, otherwise floor and tub look good. That vertical support channel though is weird for sure. I think putting fender flares on would make it loko better to hide that scarey mess...