As a prototype, the SD40-2 was the most popular second-generation diesel with sales of over 3000 in the U.S. and more than 700 in Canada. There were many variations of this popular diesel because of the long production run, with Early units representing a pre-1990 appearance and Mid Production units depicting later runs of locomotives.
Mid Production EMD SD40-2 locomotives mirror a post-1990 locomotive, with deck mounted ditch lights so the modeler can use them with their modern freight rolling stock and in combination with other modern locos. Mid Production road names come with prototype accurate detailing with regards to horn and air conditioner placement as well, with Santa Fe (and ex-santa fe, respectively) units having their airhorns mounted towards the rear and additional antenna and air conditioning units over the cab.