Shaanxi,

The standard horn was mounted on the intake manifold in 1953, and the matching accessory hi-note horn was mounted on the passenger side of the firewall (after drilling holes). A reinforcement plate for inside the cab was provided.

Nonetheless, people seemed to be very creative in choosing where they mounted the horns (in 1953 and earlier Advance-Design years). Your horns seem to be mounted on either side of the engine indentation in the firewall. That looks good.