There has been a thread running on the S scale .IO group re: ten wheelers of all flavors.  I have several pix of Southern's 4-6-0s, including the "famous" low-numbered 903 that plied Alabama rails longer than any others.  From a modeler's perspective, Varney (later, Bowser) produced the Old Lady 2-8-0 and Casey Jones 4-6-0 in the late 50s/early 60s using the same boiler.  Some claim the boiler and other features are based on the Southern Pacific T-28 ten wheeler. which does have similarities (pilot, boiler and cylinders but not cab).  I've also heard that the boiler, cab and mechanism were "OK" if modeling a Southern 4-6-0.  The recent Bachmann 4-6-0 is unrelated to the old die cast models.

While there is no "definitive" answer to the SP claim, many historians agree that Gordon Varney wanted to appeal to a larger market than SP modelers so picked features from various engines, including SP.  He went with a USRA-style tender, likely to commonize tooling with other models.

Has anyone delved into making a credible Southern 900- or 1000-series ten wheeler from a Varney, Bowser or Bachmann model?  Personally, I like the 1100-series better because of their relative "bulk" and piston valve cylinders but they'd require a different starting point than the smaller engines.  No matter which one is picked, lack of Southern valve gear needs to be addressed.

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Jim King
http://smokymountainmodelworks.com