Your description is a little confusing to be honest (at least to me) but I think this is what the situation is ...
You have a Dually van i.e. two pairs of wheels each side at the rear. The outer wheels are the "wrong way round" so the valves face inwards and are so very awkward to get to check the pressures? And that is the problem?
You can get valve extenders - straight ones on the inside wheels so you can get to those easily (and Ithink you have fitted?); For the outside wheels, you can get bent valve extenders - like the end of a paperclip which makes that valve easy to get to,
Word of warning. I fitted valve extenders to my dually and I found the bent ones tended to loosen up over time and I twice ended up with an outer flat tyre due to the extender being loose. I think you have to be careful what you buy. I found what was meant to be a benefit was anything but.
I have "solved" the problem by fitting a
tyre equalization kit that apart from interconnecting the tyres via the valves, just presents a single tyre valve at the front to attach an air hose to.