1954 Hydra-Matic booklets are listed on this page (in the 1954 section).

Here is the 54 GMC H-M manual. The GMC and Chevrolet Hydra-Matics were similar, except for the shift linkage/indicator.

Someone else might know how different the 55-1st H-M is from the 54 H-M (besides the open driveshaft in 1955).

There are some manuals listed on eBay. Search on: (1955, 55) (GMC, chev*) hydr* man*

Tim
1954Advance-Design.com
1954 3106 Carryall Suburban
1954 3104 5-window pickup w/Hydra-Matic
The 216 and early 235 engines are not "splash oilers" -- this is a splash oiler.