I stumbled onto the Lionel Trains Library web site yesterday. The link is below
They cover most Lionel Postwar trains and train accessories with pictures and histories and descriptions of each.
I enjoyed the Motive Power section on Steam the most and it is a super place to find the history of each locomotive, the features of each model, the date of production and pictures of each and what coal tender came with each.
For an example, they have a section the Berkshire locomotive that starts with the real Berkshire locomotive history and then has sections on the Lionel 726 and Lionel 736.
Charlie