up here at the top, if you go to links, then parts, the vendors who sell parts, usually sell the reproduction shop manuals.

The manuals cover all the different sizes of trucks for that year , from half ton to 2 ton or so, depending on the ton options for each year model.

for instance, Jim Carter's has these for sale:

http://www.oldchevytrucks.biz/55_66/full.asp?page=69

You would probably need the '55 2nd series(which is your body style) and the '56 supplement.

The accessory listing for 1956, has things about the doodads for that year model.

-W