Mission accomplished. I installed the dual Hella horns today. I ran some large gauge wire to them for both the power and ground. The trigger wire(s) is easy. I removed the factory horn, cut the wires, used the instructions on the side of the box, and a couple hours later I had them working fine using the included relay. The cut wires are Blue=12V(+) Trigger, Black=(-) Ground, both go to leads on the relay. I happened to have a pigtail that plugged right into the relay, but it would have been just as easy to use female spade connectors. I soldered all my connections and should have trouble free operation. It's at least twice as loud as the stock horn was. I can't wait to go honk at somebody.
These are what I used.
https://www.jegs.com/i/Hella/288/003399 ... 70QAvD_BwE