These 98 locomotives were rebuilt to replace their original ALCO prime mover with the more reliable EMD 567B engine and fan assemblies taken from retired E8s.

[7] The Missouri Pacific Railroad had a fleet of RS-2s and RS-3s that were rebuilt in their North Little Rock shops, receiving the GP12 designation after rebuilding with EMD 567 engines.

All the Alco rebuilds had the black cab/orange hood paint scheme and were able to Multiple Unit aka MU with later engines.

[citation needed] The first rebuilds: Type I — kept their steam generator, and single bulb reflector headlights; #526 & #529 kept their buffer plates for diaphragms.

Type III — The steam generator and water tank were removed and got a concrete block instead.

One of the locomotives, PC #9950, was rebuilt with the short hood removed and left with what is known by railfans as an end-cab.

[citation needed] In 1975, the Green Bay and Western Railroad started rebuilding their four RS-3 units numbers 306, 307, 308 & 309.

[13] They lowered the nose and raised the long hood for the Alco 251e 2,000 hp engines.