Do you have a tooth count on those two gears? That transmission and PTO setup was made by Clark, not Case. It's likely the PTO gears from Clark units on other tractors are the same. Oliver HG and OC3 are probably the most common. I think I have several sets laying around here. Zimmermans in PA probably has them also.
I've got a Case 310G crawler and I tried the fit of a complete PTO assembly off a HG and it fit right on.