Mikado 4501 - yes, the NYC Hudsons were big, powerful locomotives that were used
for anything and everything - including work trains (I have pictures) - depending on
needs, conditions and where they were in their "careers". Certainly you were far more
likely to see a Hudson hauling freight, say, after WWII than before it. But, again,
tractive effort is tractive effort, and if a trainmaster needed power now, and an
unassigned Hudson was what was at hand in the middle of the night, those 79-inch
drivers could haul that freight, thank you very much.
Anyway, to increase plausibility, freights consisting of 40's and 50's rolling stock would
look best - of course, freight cars last a long time, so older cars would fit in too. Just
stay away from any car built after 1957 (someone correct me if that's a bit off), which is the last year that the 4-6-4's were in service.
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What I want to see is a photo of a still-streamlined NYC Hudson at the head of a freight.
They were worked hard during WWII, and not de-streamlined until several years later.
Sometime in 1943 a Dreyfuss 4-6-4 just had to draw a freight assignment in
a pinch. The photos show how filthy they got during that period.