If I recall correctly, fellow N Scaler Claus' Approximate Time Period more closely aligns with the October 1919 ORER, which shows 290 cars in the Clinchfield (CC&O) series 2400 to 2699. 

I have the Stock Car Cyclopedia Claus mentioned-- I believe that I found it at an Ollie's (!) as part of their remainder book pile.  It has a large number of photos and some familiar names among the authors-- John Nehrich and Martin Lofton, for example.   I can't speak for the MDC model, but there are prototype photos for two other N Scale offerings-- the ancient Arnold/Rapido Iron Mountain stock car and the Micro-Trains 35000/035 series Despatch Stock Car, which is a New York Central rebuild as previously noted here and elsewhere.

George Irwin
"I still don't know what I don't know about freight cars"