Donnie, In Rick's there are 2 horn contact rings, one for tilt and one for non-tilt. The non tilt will not fit on a tilt column, I've tried.
If my memory serves, the 3 mounting points are screwed into the hub anyway, so they are grounded. Adding washers would not change that. I think the retainer ring that actually holds the cap are too short. That lead to the cap being too close to the wheel. By moving the whole retainer up, you can gain the clearance.
With the bottom have of the retainer grounded, the top halve that holds the cap would be positive.
Don't try to pry the retainer apart. There are plastice insulators that will break with too much force. The plastic insulators also act as a spring mechanism to hold the top off of the bottom. Then you can push the cap down to close the contacts.
The thingy is call the horn contact-canceling cam. The retainer is the wood wheel horncap mount assembly.