The Atlas O RR X29 is a good model to scale. PRR had slightly over 40,000 of these cars at one time. Also the Atlas O USRA Outside braced car is a PRR X26 which they had close to 10,000. They converted most of these to Steel rebuilt car. The Atlas O USRA steel rebuilt car is not as good a model in some respects as the other 2, but represents this class as rebuilt to X26c.
The Lionel Roundroof PRR car is a pretty good model of the PRR roundroof car, X31 I think. PRR did not have as many of these, but still a decent class.
After that I don't the the models of the more modern 40 ft boxcars are as good for PRR specific cars. I don't think they had any PS1s but I might be wrong. The Old Atlas sliding door boxcar was close to a PRR I have heard. Probablhy the new Atlas trainman sliding door car might be OK since the superstructure appears to be nearly the same as the old one.
The PRR was a large enough RR, at one time, one of the largest businesses in the country, they could afford to design and order unique cars to their specifications and often did so especially during the steam era.
