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You need the 1955 factory shop manual, the 1955-56 Service Guilds, and 1955-57 technical information bulletins. Finding complete sets of SG and TIB may take some effort.
CSM:
Service Guilds. The sets run from September thru August, following the sales and production year.
Tech bulletins cover same timeframe as Service Guilds.
As Glenn notes, the service bulletins are a lot more difficult to find than the Chassis Service Manual. I've set up a search string on ebay to look for these. They do show up from time-to-time, but you need to search almost daily. Asking prices for a year's worth can run anywhere from $20 to $200.