Additionally, two of the 5 × 6s were placed in an experimental center cab switcher locomotive under development by the Reading Railroad (road #87, built in 1939 by the St. Louis Car Company, or SLCC, and scrapped in 1953).

Milwaukee Road #760 (originally delivered as #1802), the first Fairbanks-Morse locomotive constructed in their own plant, is now preserved and on display at the Illinois Railway Museum.

In December 1945 F-M produced its first streamlined, cab/carbody dual service diesel locomotive as direct competition to such models as the ALCO FA and PA and EMD FT and E-unit.

[1] Assembly of the 2,000 horsepower (1.49 MW) unit, which was mounted on an A1A-A1A wheelset, was subcontracted out to General Electric due to lack of space at F-M's Wisconsin plant.

F-M retained the services of renowned industrial designer Raymond Loewy to create a visually impressive carbody for the Erie-built.

[1] F-M wanted to produce a carbody successor to the Erie-Built which could be manufactured in-house, and this required a new ground-up design and expansion of the locomotive shop at Beloit.

The Westinghouse generators in the 2,400 hp (1,800 kW) C-Line locomotives were prone to flashing over when wheelslip occurred at high speeds (such as on wet rails),[1] and the OP prime movers initially suffered from relatively poor piston life and proved difficult to maintain.

Robert Aldag Jr., who would eventually head up F-M's locomotive division, acknowledged that while the C-Line eliminated the high production costs of the Erie-Built, it failed in the marketplace due to its late entry, which he estimated was five years too late to take advantage of the sales boom due to dieselization in the US.

However, Westinghouse had announced in 1953 that it was leaving the locomotive equipment market, in part because of the generator reliability issues in the F-M units.

With the Train Master series, F-M continued production of their own road-switcher designs, but these also ultimately proved unsuccessful in the marketplace and Fairbanks-Morse departed the locomotive market.

[5] On August 24, 2020, Atlas announced that they had acquired some Tru-Line Trains molds including the HO scale C-Line model.

[9] Dealer Trainworld announced custom versions for the Long Island Rail Road, clad in other LI liveries than offered in the catalog.

[13] B units 4455 and 4456 (converted to BC Rail radio control receiver cars) were under private ownership in Calgary, Alberta but have since been scrapped in December 2023.