front or rear? if rear then there is no difference between 2 or 4 wheel drive for the rear end. and gear ratio doesnt matter on the axle. what does matter is the spline count, i.e half ton vs 3/4 ton for example. a 3/4 ton would be beefier with a higher spline count where the axle slides in and engages the carrier gears (differential)
this link got just the axle,add your zip for prices.rear drivers side 4x4