Appreciate replies so far. No foam, "hard" styrene. And small parts. 15 mm railroad models - taking Peter Pig flat cars and building stock cars and tank cars - also some gondolas but those are much simpler. Be happy to hear additional options. And, again, thanks for your replies still to come.
A wild west freight train without stock cars sort of misses the point - it was the train loads of stock cars all those cattle drives were all about and it was the drovers/cowboys that created an awful lot of what leads to Old West scenarios. Or at least that's my perspective.