[blue00gt]

If you read the Mustangworld how-to, it answers your questions:
Ok the trick to the MACH system is that there is a “Data Cable” that delivers the signal to the speakers. It delivers the signal to the speakers like RCA outputs do on an aftermarket headunit…It will provide a much stronger and cleaner signal then tapping off of a wire lead…Its located in the back of the car…That Date Cable is located right behind the MACH rack…You need a LINE OUT CONVERTER to transmit the signal to your subs through RCA cables. What you need to do is splice into the following wires (2) black wires with white stripes and (2) black wires with green stripes w/ the white striped ones being negative…
Make sure you keep the negative (-) on the converter to the same on the data cable…if your amp doesn’t have a signal sense feature you will have to run a remote lead wire. Now I know it may sound simple but a lot of people don’t know were to run it or run it to the wrong place. The best place is under the dash to the fuse box into an accessory fuse…..