The battery tray/firewall area has been patched, both floors replaced with flat metal, frame rails under floor replaced, rust hole in left rear inner rocker area, right rear inner rocker area may have had a hole filled over, diff leaks, trans leaks and it looks like welding was done in the wheel well area of the RF inner fender just above the frame rail. Looking at one of the last pictures showing the underside of the battery you can see a bumpy line between the top of the RF frame rail and the engine wiring harness. It appears that some welding has been done there. That concerns me. Do you have any pictures of the RF inner fender from the suspension side where the engine crossmember bolts on to the frame? I'm looking at the two pics of the front inner fenders for the suspension side. Does it look like there's a weld seam just below the upper frame rails on both sides?
Most everything else looks good to very good! The gas tank is nice and straight. If I were to buy it I'd patch the hole(s) in the inner rockers, fix the diff/trans leaks, replace the ball joints/tie rods/u-joints, go over the brakes/engine and enjoy it for may years as-is.
Chuck