I would opt for M.B. Klein. I’ve only ordered a few things from them. However, their prices are generally very good and their inventory is “live”. For example, if there are 3 of something listed on M.B. Klein’s web site and I buy one of them, when I view that item again immediately after the purchase, the inventory now says “2”.
Tom
[Edit: Bruce, I just checked M.B. Klein’s web site for Bachmann 2-8-0s. They have a B&O, UP, and Southern in stock.]
toytrainheaven, caboosehobbies, modeltrainstuff, ulrichmodels, trainworld, internethobbies, traintrack.net, are examples of places that might be able to help you out, Bruce. Dallasmodelworks, too. People say cherrycreek is good. There must be many more.