good reading on upgrading stock headlight wiring or 9007 conversion

RacEoHolic330 said:

Get yourself one of these harnesses to keep your headlight switch from burning up:
http://www.rjminjectiontech.com/products/headlight-harness

Then do this relay modification for your fog lights:
http://www.corral.net/tech/maintenance/foglights.html

Then read this:
http://www.candlepowerinc.com/pdfs/9004_9007.pdf

Click to expand...

So why can't the wires just be switched to match ? Won't they work that way ? What will be the cause if i put the 9007's on ? or what will be the damage ?

The headlight switch fix and the relay modification are good ideas no matter what bulbs you run. Ford messed up when designing the electrical feeds for these headlights. Here's a link to LMR's replacement harness, which I'm using:

https://lmr.com/item/LRS-14489A/87-93-Headlight-Switch-Connector-Assembly

The relay fix doesn't change the way the car draws power when the lights are off; it just changes how the power works when you turn the lights on. So I can't imagine either the relay fix or the 9007 bulbs doing anything to your battery. Of course, if you leave your lights on all night, I suspect either bulb will have an effect on your battery, relay or no relay.

Haven't done the relay fix yet to my car, and I generally avoid the fog lights for that reason.

As for the third link: I read that as saying, basically, "a brighter bulb won't make for a brighter road at night if the bulb is pointed wrong". It's not just the bulb: the reflector and headlight lens are built for the 9004 bulb. Worst case, the stock reflector and lens will helpfully aim all that extra light up into the faces of oncoming drivers and away from the road.

It sounds like your previous owner did the "upgrade" for you, in which case you'd probably need to rewire to use stock bulbs again.