The C&EI Historical Society sells a diagram book in pdf format on DVD. It contains pages from several of the original diagram book issues. Includes all the passenger equipment I am aware of that was in use at all after WWII.
EDIT- Please note that a "Diagram book" is a set of rough drawings, and includes some measurements and some mechanical specs, but is NOT a set of precise plans. The C&EI diagrams, for instance, only show one side of the car.
But in answer to the second question, the plan 7489 cars were originally purchased as the Whipporwill and Meadowlark coaches. Around 1960, they were sold to the Illinois Central- which had a series of cars that were very similar, but a different plan # and maybe a couple less seats. Actually, the old Con-Cor model is of the Great Northern coach is also quite similar other than the aisleway and restroom windows.
In the 1950s, C&EI frequently used them in service on the Georgian and Hummingbird (and quite probably the Dixie Flyer, but I don't have a consist)- so they also found themselves on L&N and NC&StL rails, albeit in C&EI paint.
