It should work. I have added handfree phone to an 04 LS, and to a 2000 Grand Marquis. I think that most Ford radios (if not all) that have the phone mute button will work. As was said, the particular pins to use change around from year to year. Yes they do all use the FCP (Ford's version of CAN) bus to talk to the factory phone, but that is not needed to make it work. The only thing that causes, is that when you hit the phone mute button, the radio says no phone and won't mute. Everything else works. (You only get the no phone message if you do have a phone hooked up, oddly enough.) I still haven't found my notes on the 04 radio. The 2000 radio had three connectors (only two populated on some models). The cell phone connections were on the 20 pin connector. Pin 10 is the cell phone in-use signal. Connect the mute output from you handsfree kit to this. Pins 12 and 11 are cellphone audio inputs (12 positive, 11 negative). Connect the speaker output from the handsfree kit to these. Sorry I don't have the pins numbers handy for the 04 radio, but other than the pin numbers the connections are the same. The CAN bus connections are present on both the 2000 and the 2004, but they aren't needed for normal operation.
Go to Radio Shack. Buy a pack of 100 ohm resistors. Wire one side of the resistor to the car's ground. With the radio connected, but pulled out of the dash (doesn't have to be turned on), touch the other side of the resistor to each pin (one by one) on the back of the radio that does not have a wire attached. The resistor will keep you from hurting anything. You'll find that one of these causes the radio to power up and go into cell phone mode. Once in cell phone mode, you can take another grounded resistor and try all the other pins again. Two of these pins will cause noise on the radio speakers. These will be the audio input pins.
BTW, I have the factory wiring diagrams and the factory manuals (from Helm). Neither mention this feature or name the pins used. They list the pins as being "not used." I suspect that the AllData stuff would be the same. This is an undocumented feature, but it is there.
