IIRC, Warrior Products has a rack that sets over the spare tire and bolts to tailgate. Would be good for a cooler. But still need to figure out to securing it to the rack, ease of accessibility, etc.
As for tools, I carry my trail tools in a soft pack and put behind the rear seat under the 'trunk' setup I have, or belted into back seat.
I wouldn't want to keep any tools up high on a rack as that's a lot of weight. Mine, I'm estimating, weighs 80#s. Its freakin' heavy. I also have a small fishing box that carries the small items: ujoint, clips, hose clamps, lubricants, brake bolts, small bolts/nuts, jbweld, etc. I also carry a milk crate that holds the bigger package fluids: coolant, water, PB Blaster, WD40, ATF, PS, brake, oil, orange hand cleaner, and serpentine belt, oil filter.