Thanks, Kevin,
I have plenty of documentation on the 1954 Hydra-Matic.
The 1955.2 is significantly different:
1954 - enclosed driveshaft
1955.2 - open driveshaft
FYI: I have an illustration (somewhere) of a 21-speed Hydra-matic (used in stone/rock quarries).
As I dimly recall, it was (basically) 2 Hydra-Matics somehow attached to reducer.
