I am very selective.
All locomotives and way cars are Santa Fe early 1950's, the only exceptions being one SP Baldwin AS-616 and a T&NO caboose.
Passenger cars are all Santa Fe except for some foreign line head-end cars for the mail train and the Grand Canyon.
Freight cars are from a variety of roads, but I have intentionally included roads, such as GN, PRR, NYC, which were friendly connections to Santa Fe.