Hi, Greg,
I know #478 had it's fake stack by 1958, I didn't know about the movie in '57. The reason there can be no doubt about the engine having it in '58 is that it appears in a Beebe & Clegg book published in '58, and there it is.
The fake stack carried by #478 was different above the diamond than that on #476, which was either modified from or patterned after #473's Bumblebee stack dating to 1950.
#476 carried that stack through most of the 50's, it defititely had it on in 1955.
#473's fake stack was patterned after #478's in 1962.
All "Silverton" cars were painted gold (single stripe) by 1955, as I recall. In 1957, the Alamosa was rebuilt into coach #350, and the window blanks in the Galley and Dining area had been opened on the car's left side. I don't know if that helps or not.