Burlington Northern retired alot of they're 20 cylinder locomotives, if not all, around the mid-80's. The SD60M's BN had were from the early 90's. The SD45's were leased back for a time in the early 90's, still in BN Cascade Green, but no BN reporting marks. They may have been on the railroad at the same time, but the SD60Ms were almost exclusively in coal service. Probably never ran together in the same train.
The BN began retiring their SD45's in 1982(?), and they were pretty much all retired by the end of 1986. Their first SD60M came, I believe, in 1989.
Ken is correct. BN SD45s were retired between 82 and 87, and the earliest SD60Ms arrived in 89. SD60s (BN had 3--all retired in 1987, and Oakway had 100) started arriving in 84. http://archive.trainpix.com/BN/ROSTER.HTM It's plausible that the SD60 (spartan cabs) could have been spotted with an SD45, it's just not likely. It was impossible with SD45s and SD60Ms (widecabs). This wreck rebuild SD45 long-hooded SD40-2 is the closest an SD60M would have been to being in consist with an SD45: (Cheyenne, WY, 2004-2005)
Or you can be like me, I got a couple SD45s and F45s that in my world, BN rebuilt to SD40-2 specs. Which is plausible with BNs rebuild programs of the late 80s into the 90s.
Thanks for the info guys. I have built a couple SD40-2's with the flared radiators, 7149, 6330 (Cat).