I took my brackets off a while ago when I replaced the rubber flaps with plastic ones and refitted them with stainless bolts.
They just bolt through the floor, would have thought that the holes may be there already, mine used to have side steps and the flaps seemed to fit round them ok.
If the holes arn't there it wouldn't be too much work to drill for them, if you undo the plastic inner step and take off the plastic trim inside on the arch you can fold the carpet back.
Hope that helps.
Jon.