Larry,

I now have a concrete example of what the ICC documentation for rolling stock would look like.  Tony Thompson mentioned the "53" section, and I dug around in my backlog of documents.  Here is what Section 53 looked like for the Southern Railway (attached PDF).  It is more detailed than I suggested, but less detailed than photographs and drawings as you might find in railroad-specific diagram books.

Hope this answers more definitively what you are interested in.

Best,

Dave

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David Bott, modeling the A&Y in '34