I have an 89 mustang and the radio harness has been cut. I want to wire up a radio but dont know what wires to use. Does anyone have a wire diagram or know what colors are for what? Thanks

 

look below where the radio is, or would be to see if there is a metal octagonally shapped box with a bunch of holes in it and two hrns's going to it.

 

This might not help you but all of the factory harnesses were cut out in my car. I had the factory premium,6 speaker sound in my car. The way I made it work in my 1988 GT was to run speaker wire from each speaker location that i was going to use"doors and dash" to the head unit area. Then just tap off of 12volt constant power for headunit memory and switched 12volts for the other power.I used the fuse box and tapped power from there as this was very easy to do.Just use a volt meter to check for the power 12v constant and the power for 12v switched .You can ground off of any secure area under the dash that provides a solid connection. Since I was installing a sub and amp I ran fused 4gauge wire from the battery positive through the firewall grommet and ran it underneath the door sill on the drivers side all the way to the spare tire well. I used a clean secure area in the hatch to make my groundconnection as well. Then I just ran RCA cables from headunit running the cables under the carpet through the middle of the car ,up under the back seat, then under the trim in the hatch directly to the spare tire well and connected it to the sub amp. It really isn't that hard to do if the factory harnesses have been cut. This allows you to clean up some of the wiring mess anyways and also use better quality wires. Then you could also solder all of the connections like I did for good secure connections. Sorry for this long response.