I'm just about finished with an Electra Glide Ultra to Road Glide conversion. I think the Road King conversion might be a bit more challenging.
I had to lengthen two jacks on the fairing harness but at least I had a harness, stereo, and all the bar controls to start with. I've spent about $1200 so far and still need paint. I'm sure it can be done.
A guy on the hdforums.com had a good thread on converting his Police Electra Glide. I'd suggest doing a search there for the thread and see what you might be getting into.
Good Luck, RT
This aircraft is intended for aerobatic use only. Sustained up-right and level flight is strictly prohibited.