Sidehill,
The 1955-59 GMC maintenance manual will have a section on the 302 and will cover all the carbs that were available from the factory. These manuals can be found on eBay from time to time and reprints are available from most automobile literature store such as Faxon Auto. Also availble is a reprint of the 1952 GMC 6x6 military manual for the 302. You should be able to find sources using a web search.
