Originally posted by JTang
You could probably splice into the existing radio's remote line lead if you could identify which one it was. This site may help you:
Dead Link Removed
The problem seems to be that Fords have a 5 volt turn on signal rather than the 12 like most other cars and components. Because of this you'll need to go out and get a Low Voltage Trigger too. An inexpensive piece you can get from Sounddomain.com or anywhere else, I'd figure.