CAN I SEE..... "FM MODULATOR"????!!!!
DING DING DING DING!!!!! CONGRATULATIONS OVRRDRIVE, YOU JUST WON A 13 PIECE STEAK KNIFE SET AND A TRIP TO BEAUTIFUL SUNNY ARUBA!!!!
The installers saw what I saw on the back of that factory unit. Sorry laidback....
with my mind on my money and my money on my mind. It looks like its either 1) use the Sportster's FM mod feature or 2) get another head unit. (wah-wah -wah-waaaaaaah)