Erik (and others who may be interested) -
To provide some assistance with nomenclature, I'm posting a diagram of a 4-wheel passenger truck from earlier in the 20th Century (I think it came from a 1920's-era publication) that I've labelled the major parts on. While it's a lot older than the one you're modelling, the basic structure of a railroad passenger truck didn't change that much over the years, so this should still apply. The main structural differences between this one and the one you're modelling are the type of bearing (friction on this one, roller bearing on the one being modelled) and the change from centrally-located brake beams (on this one) to putting them on the ends of the truck.
https://www.dropbox.com/s/0frbr7vb18...er%20truck.png
Joshua