Ross, Mister Nutbar's first picture is indeed a horse express car: I built it for him after he saw my version of the same car (the very first picture in this thread), which I built from a photo of a Grand Trunk car in a book lent to me by Mister Nutbar.
The Harriman cars would not have ever had a truss rod underframe. I'm not sure when they were first built, but they were developed by the Harriman lines as an early, all-steel lightweight car. Canadian National had quite a few wooden, truss rod cars that received steel underframes and also retained their truss rods, as well as truss rod cars that lost the truss rods when a steel underframe was applied. Some of these cars also received steel sheathing: those that lost their truss rods looked very much like all-steel heavyweights, as the arched windows on the wooden cars were often plated over at the same time.
If you want a wooden car with truss rods, yet still want to keep the car fairly short, MDC makes (made?) some short, open platform cars that you might find suitable. My LHS has quite a few of these in stock, so they may be back in production, otherwise, there should be plenty about.
I'm using mine in work service, representing older cars retired from passenger service, so the paint scheme is pretty bland.
Postal (with some windows plated-over)
Combine (with windows added in the baggage section)
Coach (with some windows plated over)
These cars scale out at about 56' in length. Note the two different roof styles: all cars are available in either style. The roof on the coach predates the other two. If these cars were in regular passenger service, they would have battery boxes in addition to the truss rods and brake gear, or maybe Pintsch gas tanks for lighting. No a/c on these late 1800s cars. You could close in the vestibules to update the cars to the turn-of-the-century era.
Glen, CNR first used the green/black/gold scheme in 1954: I believe the first cars were part of a very large order of lightweight smooth-sided cars from Pullman-Standard. Many heavyweights were repainted to this scheme, including some head-end stuff. One of the 40' steel express boxcars is shown on page one of this thread, and the 40' 8 hatch, over-head bunker express reefers also received this scheme. To the best of my knowledge, none of the wooden passenger equipment was ever painted in the green/black/gold.
Wayne