This is the first time I've seen a UP train and thought "would".
https://www.railpictures.net/photo/864070/
Neat train.
At some point in the last few years I looked into a pike sized train that was regularly pulled by an FEF with the thought of a short but prototype train for modular setups and came across UP 95-96 National Parks Special.
Best I could find online, this train was one of the later regular FEF assigned passenger trains and the consist in the picture was the off season train and in the summer it was heavy with foreign road sleepers full of tourists bound for the Rockies. I'm sure it covered in detail is some UP book somewhere.
I will say, if you are temped by this, don't look up the lines from Cheyenne and North Platte to South Torrington Neb. Daily mixed trains with E Units and PA's for power, local freights covered by EMD and Alco roadswitchers and FAs, and 2-8-2's, 2-8--0's and 4-8-2's used into the mid 50's. It's very tempting, but to do it justice you'd need a ton of space for the wide open vistas of western Nebraska and Wyoming