Quick post to answer George's question
"Valve extensions for inner dually tires
The awkward placement of valve on outer rear dual tires: why do they face inward and do they HAVE to be that way."
If you look at the valve placement, the "inside" of your outer dual is really the "outside of the wheel if that wheel was on the front or was the inside dual. This means all wheels can be the same. If the valve was on the outside of the outside dual you would need a different spare tire/wheel assembly as you can't have the valve on the inside of your fronts or inside of the inner dual and clear the brakes.