The ‘75ish and older transmissions, the governor springs and weights were different on police and on HP (high revving) engines. When looking into this for another member, the governors are the same for all 1986 A904/A999’s. The differences are inside of the valve body - for the higher shift points.
I’ve yet to look into the differences on late 70’s/early 80’s transmissions so somewhere there had to be a break between differences in valve body vs. governor.
Note: A727 and A904 (and variations) valve body's look the same at a glance - but will not interchange. It is no fun trying to determine what a "loose" valve body came out of - if you work in an area where transmission repairs take place.
In many cases, the same model transmission valve body will not interchange with the next year up (or down) without complications.
I have the A999 out of an ’84 M police car – which I saved because of its higher shift points.
BudW