The bucket outside holes are not the ones for a bench seat! look under the car and you will see a second set of holes in the brace inboard of the bench seat holes, but not through the floor - drilll through them. The inboard holes show up as dimples in the floor pan - just drill through those. I never understood why the outside brace is under the floor pan (which makes sense) but the inboard plates are above the floor pan (no sense). Suggest you use some big *** washers on the inboard studs, UNDER the floor pan. You need rubber plugs for the bench seat holes (RT Specialties has them).
