As Sheldon has mentioned, the Harriman head-end cars are of a prototypical length, while the passenger cars are somewhat shortened. These early steel cars (1909) were an attempt to produce cars to a standardised design, and were considered lightweight cars.
The MDC-style Pullman Palace cars were widely used all over North America. After the introduction of the steel heavyweight cars, some were scrapped or downgraded to secondary service, but many were “steel plated” (covered with sheet metal) and saw many more years of service. To the untrained eye, they looked very similar to the true steel heavyweights.
In this area of southern Ontario, there were many still in service in the mid-'50s on secondary lines and mixed trains, and I recall seeing them still with wood sides, too. Many were updated with steel underframes (some of these retained their truss rods, too), and, when their passenger-carrying days were over, were downgraded to work train service.
I believe MDC offered a combine, coach, Pullman, diner, and an observation car, so you could probably create a “representative” version of an SP or Santa Fe train. The window arrangements on the models may not match the prototypes exactly, but with decent paint and lettering, it should look convincing.
I’m modelling the late '30s in southern Ontario, so there are still wooden cars in secondary service. I added a steel fishbelly underframe and some underfloor details to this MDC combine:

This CNR coach retains its truss rods, but got some added underbody detail:

I even have a Harriman-style baggage car - I modified the underbody and installed six-wheel trucks:
[IMG]http://i23.photobucket.com/a