I just installed one in my 66 Dart this week. I purchased it from summit back a year or so ago. At first I didnt think it would fit but I used a piece of aluminum channel as my bracket and Im very happy with how it looks in place. Here are a few pics:
I am using this one on my '69 Dart. You can fit it right next to the radiator on the passenger side, and still retain your stock horns. This one too requires a bracket to be fabbed from aluminum L-iron. http://www.summitracing.com/parts/mez-wr100u/overview/