I have to install a horn on my 1953 GMC 1/2 ton to pass the vehicle inspection. Does anyone have any pictures or diagrams on where it should be located?

If it is the “seashell” style horn, as used on 1953 Chevrolet trucks, it was mounted on the intake manifold (there was a “boss” with mounting holes on the 1953 Chevrolet intake manifold).