I was crusing thru ebay. I saw a guy had an acution for a shaker 1000 headunit. He has a picture of the back (shown below). I emailed him and asked where the AUX input jack is. He replied that he was not familiar with the unit, but the only inputs he saw were the ones in the picture.

Shaker 1000 Headunit - Ebay Auction

 

Nice to know they are made in Mexico. Is nothing made here anymore?

 

In the Mustang the AUX button is non functional, I checked the wiring schematics for possible function and ther are no circuits tagged as any kind of input to the head unit.

The front panel is shared with several other vehicle lines and some functions may be available in the future (i.e. satellite radio, DVD gear etc.)

Hope this helps.