The movie did a fantastic job in portraying the locomotive and cars. I would use any of the Athearn standard cars (out of production - but always on Ebay) in the olive drab color.
I would recommend a set of the new Con-Cor Suburban 65’ coaches.
You can get them undecorated in the Pullman Green and add your own roadname.
These cars have interiors and lighting as well.They would look great, turn out the lights and you have a great night scene. Would look terrific in a under the tree layout.
Paired up to say a Bachmann 2-8-4 Berkshire you would have a close match. The smaller coaches also would not dwarf a smaller layout.