PRR round roof cars are very different from B&O "Wagon Top" box cars. The PRR car, whose design was used by 3-4 other roads, is a typical structure with traditional built up sides with traditional or typicla framing. The only difference is that they made a rounded roof with the sides of the roof curved around to give more height inside.
The B&O car was only used by the B&O and is a very different structure. The ribs start at the frame on the outside and go up and over the roof like a old conestoga wagon. All the supporting structure is on the outside and it is quite different from what other cars had. I guess it reduced weight and was easier to build than the other types.
The Lionel round roof car is a model of a PRR X31 round roof car. It is easy to convert to 2 rail. I just cut the lionel couplers off the truck bolsters after disassembling the truck, and then replaced the wheelsets with Athearn wheelsets. I think Intermountain or NWSL wheelsets could be used also. Then I body mounted the Kadee couplers on the car.
IN my opinion, boxcars from any road could show up anywhere. Generally boxcars handled manufactured goods. A lot of manufacturing was in the east so stuff originated there. But it shipped all over the country, so boxcars from roads in the NE would have good reason to be in Texas or Calif. A friend of mine has found photos of PRR X29 boxcars in Calif.
