EMD GP20E unit 4138, lettered for Southern Pacific component St. Louis Southwestern (the "Cotton Belt"), leads a four-unit lashup with an eastbound SP manifest through south Texas in February 1975. Its original number was 803, but when rebuilt the unit was renumbered 4033 before assuming its final number. The "E" suffix was not an official designation but was popular railfan nomenclature to designate a unit that had been sold to subsidiary Southern Pacific Equipment Company in the R8 "Capital rebuild" program and then leased back to the railroad.