Dragon - I have this
http://www.amazon.com/gp/product/B00UEGDDAY/ref=ask_ql_qh_dp_hza plugged in to my USB port in the glovebox (USB for power to the transmitter). I had some old 3.5mm extension cables lying around & soldered 1 female end (about an 8"-10" piece) into the cable from the radio to the plug (280 I believe) inside the fairing. It's soldered to the front headphone wires. I drilled a hole in the back of the glovebox to run the other extension, which is 3.5mm male-to male, to the transmitter for the audio source. This gives me the ability to disconnect it when I need to take the front off of the fairing. Go to settings & set the outputs (I set all of them) of the Boom to headsets instead of speakers. That's about it...30 minute project on the cheap.
After getting that working, I decided I wanted to be able to listen to music from a USB stick, in addition to the radio, so I got a tiny 4-port usb hub, plugged the transmitter into 1 port & the music stick into another port & I was done. The transmitter, hub and USB music stick are all in the glovebox and can be unplugged & stored in a safe place (or in your pocket) if you are parked somewhere where you are afraid of someone stealing them.
If you are not comfortable with soldering, I have seen somewhere where someone sells a 7 pin to 3.5mm adaptor, but I can't remember where I saw it. Since you have a Street Glide, you would have to buy the $70.00 cable from HD that plugs into the 280 plug & gives you the factory 7 pin headset plug. I didn't want to spend the $70+ for the cable and adaptor so I just soldered into the existing wires!! Another option would be to buy the mating plug to the 280 plug & just pin it out to the 3.5mm female jack. I didn't want to go to that much trouble!
T