Bob, I remember them, too. They looked like O Scale models on television.
With Carl Akers, Alexis McKinney (D&RGW PR Dir.) and the D&RGW all gone, The F-units will probably remain one of those Historic mysteries.
My best guess is that when the D&RGW stopped sponsoring Channel 7 news (at 10:00 with Carl Akers, Warren Chandler and Starr Yelland) the props were probably consigned to the (Literally) dumpster of History.
The question that you should be asking, is what happened to all the footage that was shot by Channel 7 for the D&RGW commercials that aired when they were sponsoring the news. They had to be local because Carl Akers was the pitchman.
Rick