Here is the 1956 Buick Service Manual, in it's entirety along with the addendum's published the following year with model year updates. Key thing to note here is that I actually purchased a clean original Manual and hack sawed off the spine so that I could get nice, crisp and detailed scans of an original. Far better than some of the "reprints" I've seen out there with crappy looking xerox copier quality. This is the good stuff, like having a real manual.
I've also included the Abridged version of the Product Service Bulletins. Lots of good tips and tricks in there. I have an "unabridged" set of these Bulletins as well in loose leaf format from a closed Buick dealership, and near as I can tell, the Abridged version is all the important stuff.