You know, reading your post I think I remember having to get longer SS bolts for the docking hardware to bolt up to my bike. I had forgotten all about that, because I put the docking hardware on close to 3 years ago and it's not something I've thought about since then...

 

Like some of the other chaps here I like to prove stuff can be fitted to earlier models than Harley say! I have a factory HID kit on my 1990 bike, but do not recommend it. It does look good, but is very expensive and has very poor beam shape on both high and low beams. High might as well not be there! The HID only works on the low beam and even with a 100watt bulb on high I cannot see anything worthwhile at night.

To improve your lighting check all your grounds, as John suggested, also consider a later headlight reflector which may give better beam shape. There are fairly cheap HID kits that will fit an existing reflector, or as already suggested use high performance bulbs.

 

get the 90-100 bulb on e-bay for under $10 bucks , have them on all my bikes and love them , helps you be seen in day light and great at night , run into same problem with my 96 ultra seems like a big change in 96 some stuff fits and some won't , have fun

 

The big reason that the detachable stuff isn't for the pre 97 bikes may be the CB being mounted under the tour pack on the older biles and there is a bunch more involved in unplugging it to detach each time. You would also need to install quick disconnects on the antenna leads. There are plugs for the rear speakers/intercom/control, CB power, CB audio in, CB ant, AM/FM/WB ant, Tour pack lights to DX each time.
And to the OP's question. Putting an HID kit in will not work correctly. The lens and reflector of the headlight is not designed for an HID capsule and the beam will not be correct and all you will do is create a road hazard glare to oncoming drivers. Making sure you are getting full voltage to the existing lamp will really help. Cleaning out the inside if the lamp housing with a bit of alcohol will help and Silverstars will help.
Putting high watt lamps in can melt the cheap thin wiring HD uses.

 

That can be overcome by using the bike's wiring to switch a relay and using new wiring to the headlight via the relay.