A slightly larger winterization hatch. (closer to a SD40 style) (note the rebuilt fan arrangement)
This was not a rebuilt version for the fans, the last group of GMD FP9s were built with two 48" fans in place of the four 36" fans and were rated at 1800 HP, being, in essance GP18s inside the carbody. They were built side-by-side with late GMD GP9s which also received the two 48" fans.