The 1954 Hydra-Matic transmission was a enclosed driveshaft truck transmission.
With respect to installation-configuration, it was basically a one-year transmission (although the 1953 GMC Hydra-Matic transmission was very similar to the 1954 GMC/Chevrolet Hydra-Matic).
Do you want to transplant a Hydra-Matic into a non-hydramatic truck?
If yes, what year and size truck?
There are many parts besides the H-M transmission itself that you would need to correctly/safely install it (and shift it) in a non-H-M truck.
You might want to put an ad in the Swap Meet for a 1954 3100 H-M frame, engine, torque-tube/rear-end, cab, and shift-linkage. I think one was recently listed here or at oldGMCtrucks.com.
https://www.stovebolt.com/ubbthreads/ubbthreads.php/topics/1159858/1954_frame.html#Post1159858
