Harry,
From 1947-1952, there was a set of accessory
dual horns (seashell style) available for all trucks.
In 1953, the accessory horn came as one horn only, a high note horn (the other, low tone horn was standard).
Here is a description from the 1953 Chevrolet Truck Data Book. The accessory dual-mounting bracket is different from that used in earlier years.
Do you have a 1953 version of the accessory installation instructions? Does it should the dual horns being mounted on the firewall in 1953 (as was the case in earlier years)?
