Checked out my first tank of gas with the Tremec 5 speed I recently installed. Went from a little over 7 MPG to 14 MPG. I believe on a long trip I should be around 17 MPG. Better yet, air flow at a lower rpm on the highway means cooler temps, lower rpm also means the wear and tear on the motor will give it a longer life.
Can't beat those results! Sounds like the way to go unless your a lazy guy like me and don't want to shift. Glad it worked out so well for ya.
Rich