Ok I know the 2004 Mustang (car in sig) uses the transponder chip, now I know the key has the RFID tag (if you will) what I am wanting to know is where is the reciever (car side) is it the ignition ring that goes around the key insertion point or is it the thing that wraps around the key head once its inserted?

thanks for the help so far and educating me!

 

It's inside the column, you don't see it. http://www.ebay.com/itm/1999-2004-99-04-FORD-MUSTANG-PATS-HALO-KEY-IGNITION-SYSTEM-ANTI-THEFT-OEM-00-01/161610415047?_trksid=p2047675.c100011.m1850&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D28772%26meid%3D9e138e5883d44bd0a3d8a8c270d08200%26pid%3D100011%26rk%3D1%26rkt%3D1%26sd%3D151441898304
The halo sends the power and picks up the signal. If you rewatch that column disassembly video, you'll see how he takes it off to get the clockspring wiring loose.

 

Ok so as far as the piece that "surounds" the head of the key is safe to mod a bit is what I am getting from your statement, thanks! going to start planing the mod to make my new keys fit!

thanks houtex!! helpful as ever!!