Best mileage tip: reduce your cruising speed. That truck is a barn door aerodynamically, and above 30 or so mph even 5 mph makes a huge difference.
Aerodynamics makes a HUGE difference!
Dad bought a 1968 truck (that I still have) with one of the bug deflectors fastened on the front. Removing that bug deflector was good for a little better than 1 and 1/2 miles per gallon!
Jon