Yeeeaah, this was the biggest problem with install. I tried and tried to get it to fit between the two front body panels, but in the end it just would not fit. My biggest issue was that I did not want to cut but holes in the exterior panels. In the end, I put the horn in the glove box. It fit just perfectly, and after drilling and cutting a bunch of holes in the interior of the box for air and flow, it fits perfectly. I also had to cut a hole in the bottom of the box for the wiring. Keep in mind that the Magnum is a bit smaller than the Nautilus. You may be able to find a spot between the front body panels to mount it. My original plan was to drill one hole in the panel that is in front of your knees, and then several small holes in the front panels to allow sound out. That may work for you. I mounted the relay in the spot where the OEM horn was mounted.