Another enjoyable series, Tom. Back in the days when I was still intending to switch eras periodically in order to run modern equipment, the MP15AC was the loco that I really wanted, as I'd already chosen the SW1200RS as my '50s motive power. I went instead with those monster U-boats shown in one of my "Now and then..." posts for my mid-'70s diesels. Athearn later came out with MP15s, but by that time, I'd decided to backdate my layout, and had begun to sell off my modern power and rolling stock. I've still got quite a few '50s era diesels, most of which I wouldn't mind selling. However, I really like the SW1200RSs and, after all the work I've done to them, find it difficult to consider parting with them. They also run really well with my Bachmann 2-8-0s, so I do occasionally run late '50s operating sessions.
Wayne