5.29s and 32-33 inch tires I could do 75-80 mph on the interstate no problem in 5th gear, 20 mpg. Speedo and odometer will of course read faster than your true speed, so take that into account.
Higher rpms within reason doesn't kill your gas mileage on these engines. Kind of like you typically get better mileage in 4th with a stock truck than you do in 5th on long highway. I guess it's because you are into the throttle less when you are near the peak or torque.
Good knowledge, glad to hear that. I definitely will consider re gearing for the right price. 👍☺