GP4.5 roof detail

[nw-modeling-list at nwhs.org]

Does anyone know of pictures that show the roof of one of N&W's GP4.5's?  I'm curious about how N&W patched the hole left with the removal of the fan.  Did they just plate over it with a square piece of steel?
Also, none of the books I have say when the rebuilding was done.  I'm guessing the '70's.  Anyone know a more exact date?
Thanks
Marty Flick
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