FYI: the dual "seashell" style horns were a truck option/accessory first offered in 1953 trucks. In that year, the dual horns were mounted with a bracket that attaches to the firewall. The single seashell horn was mounted on the forward part of the manifold assembly.
firewall mount of dual horns(photos are from an old post by Mother.Trucker's - check out the whole thread - as usual "thank you MT.)
Also, that style of horn was used Chevrolet cars for a few years - the mounting studs on the car horns were/are in different locations than the studs on the truck horns.
