The most complete reference for Postwar trains (and of course, out of print) is the four-volume Greenberg's Lionel Service Manual. I kick myself because I didn't get one while they were still in stock and the fact is that the set in my office is the only one the magazine possesses.
This is the big one, but even so, I've been surprised that there were many items for which there were no disgrams, just parts listings.
For modern era trains, the available info is pretty mixed or doesn't exist in a form for public use.
