GP9 had 1 set of battery box louvers under cab, GP7 had 3 sets. GP7 had 2 sets of lon louvers at end of long hood under radiators, GP9 had one very short set. All louvers were mirrored on each side of loco. Lots of variations as units were modified/rebuilt.
Could be GP9 but louvers under radiators at end of long hood sat GP7. GP9 would have 1 short set of louvers there. Odd there are no louvers at all below cab.
Would like to have my yard on a separate throttle but still be able to use .ain line throttle to pull into yard. Diagram for use with Atlas throttle sector would help alot.