I have a 00, F550 superduty,2WD, 7.3, 6 speed trans. 4.88 gears. I use this truck for long distance towing. At 70 MPH. I am turning close to 3,000 RPMs. I am wanting to gear up to around a 4.11. Does anyone know if this is a good choice? I am wanting to gain fuel milage but dont want to lose alot of pulling power. Truck has straight exhaust and AFE stage 2 cold air intake. The rear end tag is in so bad of shape I cannot tell the size of rear only the ratio. Does anyone know if a 2 speed is available in this size rear?