RJ, I would state that it is within the realm of being accurate. 
I will attach some photos from our NP archives from The William (Bill) Shannon collection donated from his son Harold. 
One of the photos seems to be supersaturated however the image is pretty accurate to the slide. And Willian Shannon was head of the NP motive power. Not prone to goofs.
The other photo is looking back on the helper pushing 2nd 602 east of the Cascades in WA state. 
And of Bill McKown, I would trust his research - absolutely.                                                                                 Jim Dick - St. Paul Archivist / researcher / presenter.