Santa Claus brought me Bill and Michael Raia's book A Celebration of Chicagoland Railroads, 1935-1971 and it's very well done. There's a neat photo from June 1970 at Mayfair of an 11 Car C&NW scoot lead by an A-B team of Fs. I remember seeing this arrangement a few times when I was young, years before I owned a camera and thought it was the coolest thing I'd ever seen. The book explains that the E Units from the KCS had yet to be purchased, so the C&NW teamed up A-B combinations to handle heavier commuter trains on the Northwest Line. The B unit in the photo was ex-CGW and was equipped with head-end power. The four KCS Es arrived within the year and put an end to the practice.