Adding the 6A connector was easy on the '04 since two of the three wires in the 3-place Deutsch connector are re-used, and the additional two wires (only 4 of six slots are used in the new 6-place Deutsch connector) are easily spliced/tapped from the 23-wire connector already on the bike and plugged into the HK radio. Those additional two wires (R/O and Bk/Gn) are there to provide power and ground to the modules added to the bike (e.g. XM, CB, Ipod, NIM).
Since only the Ipod module is being added, a much smaller harness is used rather than the non-Ultra overlay harness (NUOH) I used to add CB, rider headset connector, pasenger headset connector and controls); IIRC, the smaller harness is p/n 6920033. In any event, all such a harness needs to do is provide the 35-wire AMP connector to access the pin-outs on the HK used by the Ipod to connect the Ipod module to the HK radio.
The only other wiring mod I made when I installed the HK, CB, etc. was to replace the wire in pin-out 9 (W/Gn) of the 23 wire connector by splicing it to the serial data wire at the speedo; this provided the serial data to the HK so that the Automatic Volume Control will work.
Carl