English: End profile of BNSF 6327, an EMD SDP40 built in May 1966 as Great Northern 325. Above the frame, the radiators and everything forward is a standard production SD40, albeit shifted forward on the frame. The compartment behind (left) of the radiators housed a Vapor steam generator for heating the passenger cars in the train. The hand-operated shutters in that section, directly aft of the radiators, provide fresh air to the steam generator for combustion. Because the steam generator compartment exteded all the way to the rear of the locomotive, the walkway is cantilevered over the coupler, the rear steps are vertical so as not to cut into the side walkway, and the hood was given a flat end. This flat end is distinctive to 1960's-vintage EMD boiler-equipped locomotives and the extremely long DD-series freight units. Traction sand, rather than being in a cylindrical pot, is in two wedge-shaped boxes squeezed into the back corners of the hood, around the steam generator. There are no number boards on the flat back. The 6 SDP40s built for the GN had F-type tightlock couplers as seen here, whereas the 14 built for the NdeM had E-type freight couplers.