need more info.... are you meaning housing flange or axle flange?
it depends on your pinion offset, and what type of brakes you are using, assuming your pinion has a zero offset, and you are using early large bearings with brake space of 2.365".......your axle lengths will be 23" on the pass side. 18.64" on the drivers if you have a housing that is 38"
The axles will be 20.44" and 16.06" if it is 38" from axle flange to axle flange.
cam67152