The Delaware & Hudson sent eight tired RS3’s to Morrison –Knudsen in Boise, Idaho for rebuilding. The new units, designated model TE56-4A by MK, externally featured a large air filter box and a chopped short hood, While they resembled an RS3, these changes ruined the classic lines of the original Alco design. I still was happy whenever I caught a chance to get an Alco of any form leading a train.