Okay, re the observation car, Doughty's "Great Steel Fleet 1948-1967" has an image of the "Commodore" at Englewood in '49 with the "refurbished observation car 'Thousand Islands' from the 1938 '20th Century Limited." The car is in the "reverse" image of the '38 'Century,' with dark gray where light gray is and vice versa. "Thousand Islands" has a "Pullman" letterboard.
Regarding the timing of the paint scheme change, Doughty writes, "In anticipation of the arrival of the new equipment, the 1938-era cars were gradually refurbished in 1946 and 1947 and repainted (first with a reversed gray--dark on top and bottom, light gray with pinstripes in the window band, then a second repainting when the pinstripes were removed). These cars were placed in service and later integrated into the consists of the secondary trains, though for a time the 1938-40 '20th Century Limited' cars would be assigned to the second section of that train, the 'Commodore Vanderbilt' and the
Advance Commodore,' as well as the 'Southwestern Limited.'"
So the"Island"-series "Century" observation cars did run on the "Commodore" and just because I can't find an image in the original paint scheme doesn't mean they weren't found on the "Commodore." (I've seen pictures of the "California Zephyr" with both FEC and PRR observation cars...so there is always the exception to the rule). But explaining the "New York Central" letterboard may be a bit more of a stretch.
But those cars coming in the '38 scheme with "Pullman" letterboards, except (hopefully) on the RPO, baggage, and diner / lounge, does sound worthy of consideration.