The rebuilding process utilized a used EMD 12-567A normally aspired prime mover from a retired E-unit, replacing the unreliable Alco 12 cylinder Model 244G turbocharged prime mover. The North Little Rock Shops also installed a custom three-stack exhaust mainfold and replaced Alco's mechanically-driven radiator fan with EMD electrically-driven fans. Almost 600 horsepower was lost in the conversion, however this was not a concern to MP, since the RS3m/GP12 locomotives were to be assigned as yard power. This unit was retired in December 1974 and traded to GE."/>