Take it to a good welder. My front left seat bolt had ripped out of the floorboard too and there was about 3 square inches of metal still attached around the bolt. I took it to a local, experienced welder and he bent it back into place and welded it. Fixed it right up. No problems since...knock on wood. You definetly want all four bolts in and holding to distribute the forces evenly or you're gonna end up with more damage.