If you have a part number from a Shimano exploded view, try Googling that part number. I had a site from somewhere in Scandanavia that had dozens of old documents that I found by doing that. I had it bookmarked on an old work computer but didn't extract all my bookmarks before I left.

Edit. Think I found it, looks like they've updated the site.
http://www.paul-lange.de/produkte/sh...hungen_archiv/