the trucks are made from "engineering plastic", a common brand for trains is "Delrin". This type of stuff is used for bearing surfaces on automated assembly lines cycling from 50-100 times per hour. The trucks are nice detailed and an equalized, which means they adjust to rough track. I assume they have 2 rail size flanges which may not be to your liking. I am not sure whether NWSL makes 3 rail size wheels with axles that length to just change out wheels. But the bottom line is they are pretty nice trucks and very nicely detailed per prototype. A lot of 2 rail guys do replace the wheelsets with metal ones.
As for the couplers, I am not sure but I think 042 refers to 21 inch radius curves. that is is pretty tight for body mount couplers but these are 40 ft cars (sorta short), so they might work. I suggest getting a pair of Kadees and testing them. Actually the weaver couplers mount the same as Kadees, so just test the cars on your curves with the weaver couplers on them.
