Your main wiring loom installation should look something like this. It must all be wrapped, neat and orderly. It should also be anchored with zip ties or the like.
The Painless fuse box is the same size as the original factory fuse box. However, it holds 12 fuses and supports a greater load. Position this guy where the factory fuse box was. You may also locate the Painless fuse box anywhere you'd like.
The horn sounding system uses a relay in the Painless wiring harness. This is like the '64 1/2 Mustang electrical system. From '65 and up, horns are sounded directly through the horn switch. A relay takes the load off your horn switch. There is also a 10-amp fuse to protect the horn circuit.
Big-Time Protection The Painless No. 20120 wiring system offers you the protection of 12 fuses at the main fuse box, not including fuse protection elsewhere in the system. This fuse box is the same size as the original factory box for Mustang, Falcon, and Comet, with a greater number of circuits and fuses.
What's It Cost?
Chassis Harness, PN 20120: $589.99 (street)
What's It Fit?
'65-'66 Mustang '64-'65 Falcon/Comet