As the amount of line under AC wires increased in the early 2000s, some of the original class K motors went back to Portland to be modified into multisystem units. Room was made for the HVAC transformers by removing the rear cab and moving the radiator section to the blind ends of the units, but other than that (fairly significant) change there are very few external differences between a K1m & O.G. K.

As for power, the K1m has more tractive effort (thanks to the new transformer) and is rated for more HP – 7000 instead of 6500 (but to be honest the original K1s are capable of producing 7000 HP w/o much trouble, so it’s more writing down the actual HP the units are capable of putting onto the rails.)