IIRC, the two Fs are Ex SP&S (787 nee-804) and Ex CNW (788). I’ve been trying to find out what happened to 787 since to my knowledge that’s the last surviving SP&S F-Unit. From my research, 787 was last seen being sold on Ozark while 788 is still on sale.
Judging by pre-BN pictures that I’ve seen, I think their F units (seven F3’s and F7’s, iirc) were bought for passenger service alongside their sole E unit on passenger trains.
Alco PA’s would’ve been more in-line with their typical purchases, but they probably wanted commonality with their parent’s passenger power on trains like the Empire Builder and North Coast Limited that jointly operated over SP&S rails?
Minnesota Zephyr F7A #788 has now arrived in La Junta and is the third “stuffed & mounted” locomotive in town. (Baldwin 4-6-2, Plymouth ML6 and now EMD F7A) It is going to live out its days as a rental cabin at the KOA campground west of town. It has no prime mover and will be painted in Santa Fe warbonnet colors… https://youtu.be/RKAPnTKGpUY
There were two F7s on the train, and they were famous for the very long time they were cheating the reaper after their dinner train gave up and they were stranded.
I think there have been some long discussions both here and on RyPN about them, over the years…
The NYMBY’s finally got their wish when the Minnesota Transportation Museum steam went away and then the MN Zephyr was gone. The track is now totally gone between White Bear Lake, MN and Stillwater, MN. Some is a walking path.
All SP&S F units as built were passenger equipped with steam generators and 59:18 gearing. The F3s had 1600 pph steam equipment and the F7s had 2500 pph steam equipment. The 59:18 gearing follows Northern Pacific practice for passenger F units. Info from EMD Product Data.