OK, thank you! I found pictures of the 250600-250899 series, but never one of the 250350-250547. Maybe because I was looking under MP and not MI?
I bought three for a kitbashing project, and only need two, unless something goes wrong. If everything works, I might renumber the extra. The sidesill is quite different, though, so maybe not.
It looks like ExactRail did MP like they did the NP, and used a late 60s Plate C car to model a 1950s Plate B. The NP's 6000-6499 series had a straight sidesill, though, and looked closer than the MP cars.