Front and back on mine is 1/2" diff side to side, I think it was the passenger side that was higher. Mine stays consistant loaded or unloaded weight distributing on or off. I lurked on some other forums on this issue before and it seams most are within an 1" side to side for other brands. My 08 F350 was a little over 1.5" diff. My F150 was exact side to side.
When I ordered my current truck I told the dealer I would not accept the truck if it was out worse than 3/4".