It would be the same Hydramatic.
The 1954 GMC/Chevrolet 1/2 ton Hydra-Matic transmission is slightly different from the 3/4 and 1 ton Hydra-Matic transmission (that year). The 1954 1/2 ton H-M had an enclosed drive-shaft fitting and the various HM transmissions for larger trucks were made for fully open drive-shafts.
The GMC 350 transmission (2-ton truck) had a different transmission than the one used on 1954 GMC light-trucks.
1954 GMC Hydra-Matic transmissions Esoterica: larger GMC truck H-M transmissions were available 14 forward gears (this option was available on a 350 in 1954) and with 21 forward gears (in 1955) - if anyone has seen or driven one, please let us know.
