[Greg is the 1954 H-M expert]
Yes - "Looks like a factory H-M truck to me. . ' '
Yes - " . . If trans is healthy, they are pretty bulletproof."
Presumably, the truck is not now drivable/testable?
Here are photos of a 1954 3104 Hydra-Matic rebuild.If the transmission in unhealthy, good luck finding a H-M mechanic and good luck paying for their services.
hum this song as you try to decide . . . 