If you have a .pdf file of the book (as you imply might be the case), complete with photos where they belong and so on, I don't understand why you even want to try an on-demand publisher for an actual bound book. My understanding has been that most publishers don't want to touch a job calling for less than a thousand copies.
Wouldn't it be a lot simpler to burn that .pdf onto a CD?
True, you didn't give an indication of the number of pages that are involved, but I know that the entire '68 Micro Journal (11 years, 8,100+/- pages, including full color front and back pages, all in .pdf format) easily fits on 3 CD's.
Once a master is completed, CD's easily, cheaply, and quickly fulfill any on-demand requests.