Depending on the year of course ....Ours look like this :
http://i7.photobucket.com/albums/y25...adunitrear.jpg
1. 10 Disc changer output
2. Output to infinity amp
3. Antenna input
4. Antenna input (from tailgate glass) (3000gt diversity antenna)
5. Radio plug ( this plug looks to have speaker connections to the rears and doors But the infinity HU has no output to it.)
6. Steering wheel controls (some of these will have 2 wires not in 97-99 though) The second connection if available mutes the radio....