The horn location on the intake manifold of the Chevrolet 216 six cylinder changed position with the addition of the accessory oil filter. This oil filter was attached to the front of the intake manifold. A special shaped horn bracket was necessary to move the horn forward away from the filter. This bracket was included in the box with the new oil filter package.
From 1947 and older, even the 3 speed transmissions shifted on the floor. There was no column shift. Without a shift box on the steering column, the oil filter could be placed on the rear of the intake manifold. Thus, the moving of the horn forward does not apply during these early years.
The attached photos show the two styles of horn brackets used between 1948 and 1953. On 1954 and newer the horn is attached to the radiator support.