I would sand around the areas to expose the good metal then stop the spread of the rust with Navel Jelly, it removes and converts rust to inert metal.
It WILL remove paint so be careful of where it goes.
You can then rivet sheet metal patches on the holes, and paint.
Add a bed mat to hide the patches.
Bed is only held on by 6 bolts in the bed and then 3 screws on the filler neck, the tail lights can then be unplugged from the harness and the bed removed.
With bed removed you could cut out bed sections and weld in(from the bottom) metal patches, then fill and grind the top side and paint, it would look like new.
Last edited by RonD; 09-05-2014 at 10:08 AM.