I wasn't suggesting using the Erie diagrams as drawings, just pointing out they were there. I am reasonably sure there are some decent drawings out there in old magazines, just need to locate them. F&C made Stillwell resin bodies in HO, so they must have found drawings somewhere.
I would be with the folks suggesting etched sides- this seems an ideal project for double layered sides in order to get the depth of the windows and arches.
I am tempted, to tell the truth, to take a shot at making the roof out of wood. Something of a pain, but I would need all of 18" of it. Or have a custom router bit made up, and go into the Stillwell roof business. Could probably net $5, maybe $10 a year making roof blanks.