Indicating gage for internal gear dim betwen balls

[gearman1234]

I am looking for an indicating dial bore gage for checking dimension between balls for internal gear. The existing gages in the market are very costly and are relevant for only one gear data.
Just wondering if we could convert the standatrd Mitutoyo dial bore gages to check the dimension between balls for an internal gear.
We have spline gage for the part but indicating gage will help us to know the actual size of the gear and set the machine accordingly.