If it is a USA truck, it had a horn from the factory.
What year truck are you referring to?
47-52 had a “trumpet” (klaxon ? style) horn mounted on the forward-top of the intake manifold.
1953 had a “seashell” horn on the intake manifold.
1954/55st had a “seashell” horn on the front of the radiator.
47-55st had accessory dual-tone dual sea shell horns mounted in different locations, depending on the year.
