From GN equipment diagrams:
length coupler face to coupler face: 103'3 1/8" or in HO 14 1/4 inches
overall wheelbase: 91'2" or in HO 12.56 inches
If you're interested on spinning one on a turntable, add a bit (say a scale 33") to the above length. Might I note that models might have a different (longer) length because of larger wheel flanges on the drivers and extra distance between locomotive and tender.
Hope this helps, Ed