I've got Tony's book, and those cars surely look the same as the one in the picture of interest.
I'm pretty confident in my scaling from the photo. I found the center of the car, and measured to the inside end. I also measured the spacing of the journal boxes. Using the known dimension of 20' from the center to the end, I came up with approximately 6 3/4 feet. Which is interesting, because the photos in Tony's book show trucks that appear to have more typical spacing of probably 5' - 6". Strange.
UP 25218 has 164 brothers in the series 25000-25296 in the January 1939 ORER. So, about half were still running. I wonder how many of those had their original trucks. For that matter, I wonder how many other sheet-metal trucks were running then.
Thank you, all, for considering my questions,