RamblerDon,
The low-coupler and high-coupler 2954 boxcars are legitimate. I don’t recall why two different versions exist, but it’s not just with the 2954 cars. For example, the #227 0-6-0 switcher and #228 are identical except for the coupler height.
In answer to your question, the cars can be disassembled. On the underside of the car, at each of the four corners, you’ll see what looks like the head of a nail. These are long knurled dowel pins that hold the car ends and car body halves together. Extracting these pins will allow the two halves of the car to be separated, giving you easy access to the brass pieces that hold the trucks. But I urge you strongly not to do this. These cars are made of a brittle plastic commonly known a Bakelite. You could very easy break the car’s body trying to extract the pins. Given that the cars appear to be completely original, I recommend that you leave them as-is.
