This measurement is made by laying a straight edge on the edge of the cowl vent(as flat as possible on the cab) to the farthest edge of the lip that the hood lays on.
Military = 3/4 inch, Civilian 2wd = 1/4 inch. This is why the hood doesn't fit quite right when a civilian cab is used. The angle is NOT the same.
Shows the difference between the radiator support bar bracket.