EMD's GP 7 & 9, recognition of

[toptrain]

As you can see this thread is all information about the GP 7 & 9 series of locos. Now the F series of locos also had different phases. And I don't know anything about them. I know The F3's had high and low fans, and it ends there. Does anybody know about them. That would be a good thread but I can't do. Don't know anything about them.
frank