[Jack21]

Pretty much wherever you can find some room near the front of the car. Trak, Pep Boys, JCWhitney variety will work. Euro horns will work. An Oo-gah horn will work (it is a Ford, isn't it?). Someplace protected from direct water spray into the horn interior, and out of the way of everything else. They (It) can be mounted to the fiberglass if you remember to run a ground wire back from the horn frame to a chassis ground. And virtually all horns work off of a relay. The relay control side completes the ground (switched ground, like courtesy lights) through the steering column horn button to the frame. The power side goes to the horn.

Cobra horns are typically used to 1) beep at other Cobras, 2) beep at waving females, 3)beep just once annually for safety inspection.