Scott H. Haycock
There is a plan for car 21329, series 21188-22187. It is in the sept. 1989 issue of Model Railroader.
Another car, number 19191 in the January, 1992 issue of Mainline Modeler, along with a construction article.
The best source would be volume 13 of the Railway Prototype Cyclopedia.
I'm searching for drawings for these cars. I checked with the historical society and they don't have them on file. Really looking for ends and roof drawings so I can make a pattern. Thanks