That must be the antenna tuner interface plug...LOL
I think it'd be pretty easy to figger out if you open it up.
The ground is simple, then you need the audio amp input. You might also find it's not possible, because the head unit needs to sense the tape player....

Ed


Yankneck = Yankee ingenuity with Redneck stupidity.
"How can I break it better?"
89 Raider 3.0 w/ 31's for now