The 1947-53 Advance-Design single standard horn was mounted on the intake manifold, forward of the carburetor.
The "clarion" style horn was standard from 47-52 (
and was used in earlier years).
The "seashell" style horn was used in 1953 (on the intake manifold)
The single seashell style horn was attached to the forward side of the radiator frame in 1954/55 (this frame was designed for the attachment of the single horn or the dual horns).
The accessory dual horns were available from 47-55.
From 47-52, these dual seashell-style horns were
mounted on the firewall on the passenger side (or, they were installed in other interesting and inventive places chosen by the dealer or owner).
In 1953, the high-note seashell horn could be added as an accessory and,
I think those dual horns were attached to the intake manifold.
In 1954/55 the dual seashell horns were mounted on the
forward side of the radiator frame.