The last new road locomotives purchased by the Reading were a set of 20 EMD GP39-2s numbered 3401-3420, arriving during November and December of 1974. These 2300 horsepower turbocharged locomotives were delivered new in the "Reading Green" paint scheme, and were very similar in appearance to the 3671-3675 GP40-2s, including their snowplow pilots. However, there were some readily apparent distinctions - the GP39-2s had two cooling fans on the rear of the roof, while the GP40-2s had three, and there were noticeable differences in the dynamic brake "blisters" as well.
The Reading's GP39-2 locomotives were used in mainline through freight service all over the system, basically as replacements for the aging GP30 and GP35 locomotives, which already been in service for 10 years or more at the time by the time the GP39-2s were delivered. All of the Reading's GP39-2 locomotives were conveyed to the Delaware & Hudson upon the formation of Conrail, where they were renumbered to 7401-7420 by painting a "7" in place of the "3" on the hood.
MODELING NOTES: As noted in the text, operationally, these locomotives could be seen in mainline service all over the system, both in pairs as well as mated with older four- and six-axle power. There have been several articles in the model railroad press about kitbashing a Reading GP39-2 from various EMD hood units (most using a GP38-2 as a starting point); however, kitbashing may no longer be necessary, at least in HO scale, with Atlas' release of a GP39-2.