I'm in with a big block (8.1L 496) ... and 4.1 rear end.
I put a mid-ship replacement tank on to help with the
distance between refills. Out in the south west it is better
to start looking at the 1/2 tank left point.
Keep TV tuned, run both truck and rig as light as possible (re-visit
often), keep tires at proper inflation levels. Build a buffer in to
your gas budget for trips. I set cruise control at comfort RPM for
the Vortec/Allison combo. Work on smooth starts and stops (i.e.
plan ahead and stay involved). Keep an eye on the gauges. Learn
not to rush.
Know that many of us are in the same situation... I prefer sticking
to the flatlands unless I have a long enough time off to get to the
ocean.
Your MPG sounds good to me.
Charles