@Point353 thanks, I looked at those, I have a bunch of old RR bodies to work with, but they all have that distinctive Santa Fe sill and the window spacing will be off. I'm not sure I want to put all that effort into something that won't look right at this point...
Otto K.
It does depend upon your definition of an acceptable "stand-in".
Can you tolerate something that looks good from three feet away or must you have a museum quality piece that can stand up to scrutiny through a macro lens?
Or, if you can't have that museum quality model, would you rather have nothing?
I suggested starting with the Rivarossi observation car since most of the windows are a larger size/length as on the prototype UP car.
However, if the side sill is going to scream "Santa Fe" at you, then it won't do. Everyone has a different noise that annoys them.
Likewise, if the window spacing has to be spot-on perfect.
Out of curiosity, how would you approach this project?
For example, is fabricating new sides (and perhaps one end) to apply to a Micro-Trains heavyweight car something you could attempt?