The shells are designed to be used with the Kato SD40-2 Chassis.
In the early 1970s the Milwaukee Road operated two commuter rail lines in Chicago: the Milwaukee District / North Line to Fox Lake via the Canadian Pacific's C&M Subdivision, and the Milwaukee District / West Line to Elgin via the CP's Elgin Subdivision. The operation of these lines was subsidized by local transit agencies. In 1974 two local agencies, the North West Suburban Mass Transit District and the North Suburban Mass Transit District funded the acquisition of 15 F40Cs for use on the Milwaukee lines. The locomotives passed to Metra on the latter's creation in the 1980s but continued to operate on the ex-Milwaukee lines.
Decals for the more modern Metra Paint scheme can be found here: