Change Differential Gears to new Ratio?

Has anyone changed the differential gears in their MH to a different ratio? Our 1999 Brave is geared way too low for how we use it and my thought was that I'd get better mileage with a higher ratio. Now at highway speeds the engine is running around 2000 RPM and it has enough low end torque to pull stumps easily. I'd gladly trade a slower acceleration off the light for better gas mileage and a quieter running engine. The axle is a Dana model, 80 I believe.

Thanks!