GR84T8,
What year shop and assembly manuals do you have?.
The reprinted Factory Assembly Manual is, for the most part, a depiction of the 1954 models.
Your question was posed several months ago. The '54 horns (and maybe '53, too) are mounted on the radiator support. And, there are single and dual-horn mounting holes found on the '54 radiator support (and maybe '53, too). On earlier years, the single horn mounted on the intake manifold - your question seems to be "where do dual horns mount on pre-'54 (pre-'53 ?) trucks?".
I cannot recall what the earlier dual-horns looked like and where they mounted. Someone posted pictures and very clear information. Maybe they will respond again.
Do you have pictures of the horns that you could post? It might be helpful to know the style of the horns (and the type of mounting brackets).
Good luck, Tim
