If you will be pulling a trailer with an automatic then I would add a trans cooler, heat is what kills automatics, and towing generates lots of extra heat.
MPG sounds low, my 4.0l does 15-16MPG around town with canopy and close to 1,000lbs of tools in the back.
Make sure engine is getting up to correct operating temp, 200degF, just below 1/2 on the temp gauge.
Many replace thermostat with a 180degF which lowers MPG, stock t-stat is 192 or 195degF.
Look at a spark plug, if it is blackish then engine is running rich, run some Seafoam or similar injector cleaner in the fuel tank.
Also check for exhaust manifold leak, a leak sucks in air, O2 sensors sees that as Lean exhaust so computer adds more fuel than is needed.
Your fuel system has 70psi of pressure, run hands on fuel lines where you can and smell for fuel, a little leak can lower MPG and not be noticed easily.
Check the drivers door sticker to see what axle ratio you have, read here: Ford 7.5 & 8.8 Inch Axle Tag & Door Codes
3.73 is the most common, it gives reasonable MPG and reasonable towing
3.08 gives best MPG but sucks for towing.
4.10 is great for towing but less MPG at highway speeds