And those boat-tailed observation cars went on the National Limited to St. Louis.
There was a pair of similar boat-tailed observation cars that ran on the lightweight Columbian to Chicago in the late '40s - early '50s, but that had different window configuration, particularly on the rear end, where the spotting feature is 3 closely-spaced windows instead of the 4 that these 3 NYC cars have.
Bachmann makes a boat-tailed smooth sided observation car with 3 closely-spaced windows in the rear, but I don't think the rest of the window match the B&O Columbian cars. But, either makes a pretty good stand-in.
And the Columbian used F3 diesels, geared for passenger service and equipped with steam generators. The Kato F-3s do have the steam generator details on their back roof panels, so are proper for the Columbian and also the Ambassador in the early '50s. E units are proper for the National Limited.
Once the Capitol Limited, Columbian and Ambassador started getting combined, the observation car was a square ended silver car with fluting above as well as below the windows, with the fluting wrapping around the rear end. There is a model of that produced by ROWA, often available on eBay.
By that time, the Capitol Limited, and whatever it was combined with at the moment, became a mixture of silver fluted and half-fluted cars, plus smooth lightweights, and "stream-styled" heavyweights of various descriptions, painted blue and gray. You would need to be a really picky B&O historian to look at a train that is generically "1950s-60s era" and say "That car doesn't belong in that train." (But there really are some of those historians.) The dome cars are the most noticeably incorrect, because the fluted ones that ran on the Capitol Limited were really "different", with the slopes of the windows on the opposite ends of the dome being quite different. Having ridden in the prototypes, myself, I do notice - but I don't feel compelled to mention that to anybody running stand-ins for their model trains.
The last "pretty" train on the B&O was the Columbian, with a set of matching smooth sided lightweight cars painted in blue and gray. I am still working on making a prototypical model of that. Some cars are "close", but need work. Others need car sides totally replaced to get close.