Over the years there have been a number of companies that have produced passenger car sides for S-scale. These make it easy to create a model of a specific prototype passenger car without the company having to go through the expense of creating a complete, operational model. Historical information is captured here as well, because you might come across these on the secondary market.
The December 1989 issue of the NASG's The Dispatch has an article by Stan Stokrocki about modeling passenger car sides, in which he describes three different methods for modeling Delaware & Hudson passenger cars.
In 1990 Tom Hodgson announced cast-plastic passenger car bodies that were made from spliced and detailed American Flyer bodies. They offered a 64' heavyweight baggage/RPO body, a 72' Budd streamlined baggage body, and a heavyweight coach with paired windows body.
Back in the 1980s, this company sold corrugated or smooth-sided blanks, into which the modeler could cut his or her own windows as desired.
This company carries silk-screened sides. Contact the company for a product listing. No web site. Money order, checks, and PayPal accepted. P.O. Box 4-4-2, Rutland, MA 01543-0442, 508-886-4848 (8am-8pm EST); e-mail.
This company was based in Springfield, Illinois. In 1990 they announced their project to produce photo-etched brass overlays designed to convert American Models passenger cars to the 1938 NYC 20th Century Limited. Nine distinct sides were made so that a full set of 20th Century cars could be modeled. These included the following cars: an Island-series observation, dorm-lounge, RPO baggage, tandem diner, 4-4-2 Pullman, 10-5 Pullman, 17-roomette Pullman, and a 13-bedroom Pullman. The modeler needed to remove the cast-on details from the AM model, and remove some plastic to allow for the new window openings.
This company currently sells a number of S-scale passenger car sides. These are intended for the American Models passenger car. They offer sides specific to a large number of railroads. If you don't see one listed, contact the company, preferably with some prototype information, and they will be happy to produce a set of sides for you. Below are a few photos of models that Dick Karnes has created using their products. Union Station web site.