As per GM, accessories during the 1930’s through mid 1960’s were the extra cost items sold and installed by the approved dealer. The truck was prepared for these during production so the dealership could later add them with less effort.
As much as possible GM would punch holes, attach removable plates, press in dimples, etc. to help the dealership in placing the accessory in just the right position. Several accessories using the pre-placed holes or dimples in these early Chevrolet and GMC trucks are the right side taillight bracket, fresh air heater, radio, front bumper guards, cigarette lighter, arm rest, glovebox light, and windshield washer.
Options were added at the factory. They were more difficult to install by individual dealerships and were therefore placed on the vehicle during production. This included items such as a chrome grille, 4 speed transmission on 1/2 and 3/4 ton chassis, double action shocks, tinted windows on 1953-55, two speed rear axle on larger trucks, double action fuel pump, hydrovac power brake, etc.