Phil,
Since nobody has touched upon the differences between the "Alamosa", "Durango" and "Chama", I will try.
As mentioned before, these three parlor cars were rebuilt during the same modernization project and accounts for the similarities. The "Gunnison" and "Salida" were also rebuilt during this project for the Shavano trains...
If you look closely at the three San Juan Parlor cars, you will see very subtle differences between all three, making them each unique.
The Chama has rounded upper corners on the windows. The others do not. The Chama is also missing a small section of the Belt Line on the fireman side of the car, between the galley windows.
The Durango and Chama have a small window in the galley, the Alamosa does not. The Alamosa also has an extra window on the Engineer side of the car, opposite from the Galley.
The Alamosa side height is approximately 1.5 inches taller than the Chama and Durango
The electrical conduits on the roofs are all different, as are the Clestory windows in the roof. Even the roof profiles are all a little different per each car.
The Queen Posts, Needle Beams and Truss Rod configurations are all different. Even small differences in the end platform and Drumhead brackets…
I could keep going, but I’ll stop... I'd have to refer to my building notes.
Kevin