Look at this EXCELLENT website for current display locations of the UP 6900 series DDA40X Centennial diesels:
http://www.steamlocomotive.com/centennials/ Look at this posting for a few other websites with photos of those UP Centennial DDA40X diesels: http://www.trainorders.com/discussion/read.php?f=1&i=50912&t=50894
(I have found that Evan Werkema is a VERY KNOWLEDGABLE railfan!)
The Display locations of the UP Big Boy STEAM LOCOMOTIVES are listed here: http://www.steamlocomotive.com/bigboy/
This info should be what you are looking for!
Daniel