If one looks at the window arrangement of Unitah #50, the paired arrangement looks the paired arrangement of a Pullman car.
Look at this photo by Otto Perry to see what I mean:
Denver Public Library
Also, looking through the windows, the seating seems to have high back seating like a Pullman would have had. Could the #50 have been created using parts from the #1 and one of the former Pullman cars?
Why? Maybe a wreck? Condition of the car?
When the steel sheathing was done, was #50 found to be in worse shape than one of the ex-Pullman cars? And the numbers were swapped to keep the accounting department happy. This type of situation has been known to occur on other railroads.
Questions and not answers.
BN