just curious....
is your new tire gauge a standard truck pressure gauge?
i ask, because the regular pressure gauge is kind of a t style head. works both directions.
iirc, on my rear tires, the inner air stem faces out, and the outer air stem faces in, in holes 180 degrees apart on the rims.
i check pressure in between both tires and use both sides of my t style pressure gauge in the process.
a new pressure gauge with a single head may not work on duallys.
https://www.iowa80.com/pd/dual-head-air-chuck/00690/