I made my own out of 1 inch stainless angle and welded them to the floor. I found that the "universal" brackets mount too high. I had to modify the brackets on the seats as well. Otherwise I was brushing my head on the headliner.
Mine came with the brackets (craig's list ) so I just cut them up to make them work.Out side by the doors there basically flat to the floor, no feet, and bolt to the stock location. The inside part of the bracket has feet to level the frame. My car had a bench so no inner bolt holes, drilled holes and used plates with nuts welded on for the inner supports.
I welded flat bar to frame of the seat and then drilled and tapped the flat bar for stock seat sliders. Kept the seats nice and low. I used two sets of bench seat sliders. With this set-up you can use stock mounting hardware and locations.