I have a calender picture of a GN switcher that looks like a EMD sw8 but longer and with 2 exhaust stacks. It’s sitting on the turn table at Superior Wisconsin in July 1954. The caption say there were only seven ever built. The color is green and orange modified Empire Builder type. Can anyone one tell me what it is?
Based on your description, your locomotive would be an NW3, a lengthened switching-type locomotive that was equipped with EMC road trucks and a steam generator. These were used in branchline passenger service originally, and later for general light road use and switching. They had 1000 hp. Two still survive-the 181 is on display in Whitefish, Montana, and the 179 was doing industrial switching somewhere out east last I heard.
The number of the loco in question is #177 And the caption says it was used in freight and switching duties but they did not give the make. The number puts it right between the numbers you gave so you must be right on.