The Chevrolet & GMC Hydra-Matic transmissions on 1/2 ton trucks were quite similar in 1954. Here is a GMC manual (thank you, again, Keith Hardy):

http://chevy.oldcarmanualproject.com/gmc/54hdtmm/index.htm

Here are links to other 1954 Chevrolet Hydra-Matic service manuals on Keith's web site (6 parts/pamphlets - look at the links at the bottom of the contents page to the other parts/pamphlets):

http://chevy.oldcarmanualproject.com/booklets/5430smindex.html