http://www.hdforums.com.au/Default.aspx?tabid=71&forumid=12&postid=106994&view=topic

J just completed this mod on mt Street Bob. It has always annoyed me, having the key switch for lots of reasons. I did this mod it's as easy as. I picked up a soft tail switch the trickiest bits were

The hole shouldbe 48 mm

extend the wires from the key switch by 5 or 6 inches and you can use the switch connecter rather than spade fittings.

Great mod and very cheap