Drew,
Got it; prior to mid-July, 1932, all of the grill portion of the commercial/truck one-piece radiator/grille assemblies were painted black regardless of the color of the cab, hood, and radiator shell. After mid-July, the paint treatment of the one-piece commercial/truck radiator shell/grill depended on the color of the hood and cab. If the cab, hood, and radiator shell were in either the golden orange or vermilion red color, the grill continued to be painted black. If the cab, hood, and radiator shell were blue rock green or mountain brown, there was no separate paint treatment of the grill. (Obviously the grill was painted black when the cab, hood, and radiator shell were painted black.) So the answer is no, sea gull gray was not used on one-piece commercial/truck radiator shell/grill assemblies.