I have a 75 Supercab Project going on and figured I'd take some pics of how I added the speaker wire to the doors. While it's not the "stock location" and won't work with a original harness, it works pretty good. I did the same thing with my blue 77 when I restored it. On the inside of the dash below the pillers are some large holes where additional wires are leading and you can use those to run the speaker wire. On each top door hinge there is a small hole that you can feed the speaker wire up through and then you can reach in with 2 fingers through the large access holes and pull the wire through. I then had the door panels off and drilled from the inside of the door a hole bascially in the center of the top door hinge to run the wire in the door. I put some shrink wrap on the speaker wire to protect it in the holes and the wire won't catch on the hinge. I have had the wire in my blue 77 for 6 years now and nothing wrong with it. Here are some pics. Hope it helps.

Drivers side inside the dash


Drivers side top hinge where the small opening is (no drilling)


Drivers side inside the door where I drilled the hole


Wire leading in through the hole. Wire won't catch on the hinge when the door is shut.




Then I just repeat for the Passenger side.

 

--I'l have to check my 73 out as i have been looking for a way to run wires. When I got it somebody had drilled though the door , then just taped the wires to the jam, pinching them with the door every time you closed it.

 

You really wouldn't know there is a small opening at the top hinge that can be used to route a wire. It's a little more work just to take the instrument cluster out and the glove box liner, but worth it IMO to get a clean access without having to take the doors off. If from factory, the speaker wires would have been routed lower in the door jamb where there is a dimple in the door jamb between the two hinged area. With the doors on, I don't there is enough room to drill a hole and I don't think a small right angle drill can squeeze in there. Taking doors off is a PITA, so who wants to take a door off just to run a speaker wire. If the doors are already off than it's a good time to maybe get a original speaker wire harness and make it original, but this other way is a good alternative.

 

Yeah I have owned four 79s and a 79 bronco that all had the factory speakers in them and i remember that wire. I just don't remember it that well and when i bought the 73 with speakers i never thought about it until i started fixing things. Taking the instruments and compartment out is no trouble as i have them out now correcting a lot a former owner caused problems. So i guess now is the time to at least put the wires in place.

 

On my old truck (77 cab) there was a hole in the cowl to run the wires out into the hinge area. On my new truck (79) there wasn't. Either way, here's a little trick I found for routing wires through sheetmetal. Go get some vacuum hose, fit it to a rubber grommet, and then pull the wires through the hose. Very waterproof, and doesn't seem to pop the grommet out as easily. Here's a few pictures from my trucks:

 

Now that's a good idea