So, here is what I know. Could a K4 pulled the Crescent Limited between 1925-1934? Answer is yes, but not all the way to Penn Station because of the Kaufman Act. The Kaufman Act banned steam locomotives from Manhattan after June 30, 1908. More than likely, an electric locomotive on the PRR would have pulled the Crescent. However, Railroads have/had “Standard Operating Procedures” (SOP). One of the first procedures is to keep the trains running. That’s why we find unusual pictures of freight locomotives pulling passenger trains, mix-match passenger cars, or other “oddities.”
As for passenger cars, from 1935-1949, the railroads were dealing with the Great Depression and WW2. For the Southern, heavyweight passenger cars were Pullman green. After 1946, the script used change from Roman to Gothic (Blocked) except for the business cars, they remained in Roman. L&N, and The West Point passenger cars were in Pullman green as well. They both changed to a shade of blue in the 50’s. I believe that PRR were Tuscan (hopefully PRRRONBH can confirm). Stainless steel cars started showing up on the Southern in 1941, for the Southerner and the Tennessean. In 1946, the 5 participating railroads reached an agreement to re-equip the Crescent. Eight different car types were use: baggage-RPO, baggage-dormitory, 2 chair car configurations, dining car, 2 sleeper configurations, and a boat-tail sleeper-lounge observation car. Three different car-builders were used: Budd supplied the coaches and dining cars, Pullman-Standard the baggage-RPO, sleepers, and observation cars, and ACF the baggage-dormitories. Because of the high demand, it took the car builders 3+ years to fill this order.