I like them all, but my personal favorite is the 1939 version of the Hiawatha streamliners. These are the ribside cars, orange with a maroon stripe, with the Beaver Tail observation with the Buck Rogers fins on the tail. They were built to go with the F7 4-6-4.
I do run heavyweights a lot. In fact, a string of heavyweights behind a black Bi-Polar is on deck for this weekend's open house at the museum.