In order to have full 4wd capability, you would need to gear the front the same ratio as the rear. IF you only want 2WD then NO, you do not have to do anything.
A few old sand players did run mismatch gears. (410 fronts 456 rear) They insist that the faster turning front wheels would pull them thru a turn in the sand much better then matched gears, Never tried it myself. Got to rase hell with the drive train even in sand.