I think you're talking about the same bracket I had, the one with the aluminum perch welded to the middle of a "C" shaped bracket? You take out the front two bolts and use the two longer ones that come with the mount. I would STONGLY suggest using a heavy duty stud instead of the typical 239 style stud that you would normally use on a standard whip antenna. Those are gonna eventually come apart and that Predator will end up on the side of the road. It's a heavy antenna, and with wind resistance and bumps in the road, will put a lot of stress on your mount. Just keep a close eye on your bracket/mount and watch for cracks.