Ryan-
You get the points for a definitive answer to the question with the info you sent. THANKS! Hopefully I will be able to return the favor someday.
For others who might be curious- Monon began replacing "The Hoosier Line" slogan on the sides with "Monon" in late 1951, per the article in Mainline Modeler (May 1982). A hypothesis on my part is that the 85 A/B, the black/gold (but still steam gen equipped) locos that were wrecked at Monon, IN in the fall of 1951 were probably the first to receive it, and it was then done on similarly painted Monon freight units when they came in for regular painting in future years.