I am sure that there were different governors available depending on the engine and axle ratio. The turbo 400 definitely had different governors. The 400 had a habit of stripping the teeth off of the plastic gear and I used to frequent the auto wrecker near me and would grab a used one from a core transmission. One time I did get one that changed the shift points to a slightly higher road speed. I wouldnt have noticed except it was my own truck and I felt the difference.
in those years different axle ratios didn't change the transmission (except speedo gear of course) itself but different versions of a transmission would be used depending on which engine was used or which specific model car it was going into. For example on a 69 GTO there were 3 different versions of the auto trans option (TH400 but same concept with TH350), the differences being in the governor, torque converter and clutches etc: the standard engine used one version, the Ram Air engines (3 and 4) used a different version with tighter shifting feel and the optional 2 bbl engine version shifted earlier to reflect the lower power band of the engine.
The way to get a sense if they varied is by transmission pick codes being used in a given car, to know for sure you need an MPC to study the part numbers of each component. If auto transmissions have the same 2 letter pick code in a given year then the internal components will all be the same.
