How do you change the gears in a 1954 Willy's Overland Pickup to a higher gear ratio?

At the moment the truck's max speed is about 45mph. I need it to go 70-80mph. Does anyone know how to do this?How do you change the gears in a 1954 Willy's Overland Pickup to a higher gear ratio?
With out changing the transmission (or all the gears in it) change the final drive (the differential) or rear axle assembly.How do you change the gears in a 1954 Willy's Overland Pickup to a higher gear ratio?
U have to change the RING GEAR %26amp; PINON you mostlikely have a gear ratio of about 5.56:1 you need about 3.90:1 to run 80 comfortablely there on store online that sell them and also an army surplus store may bea able to help U.