I just installed a new air horn under the hood but can not find a way to wire it to the switch through the firewall sugestions please thanks.

 

there is a big grommet behind the drivers valve cover (kinda under the master cylinder) and it comes out just above the brake pedal.

 

i had the same problem with my train horn.. i ran it neatly through the door jam(not in the way of anything) and notched out the weather stripping. was easy and fast. when i do get time i will re-route it though thru the fire-wall...

 

Don't run it thru the firewall - just tap it into the stock horn wire or relay under the hood.