I autocrossed for ten or so years until I got bit by the Fireturd bug. I started out with a VR6 Jetta, then stepped up to a Chevy Cobalt SS/SC for more torque out of the corners. I ended up buying the Corvette to make the autocrossing more interesting (and boy is it wayyyy more interesting with rear wheel drive and no traction control). The point of the story is that I bought a set of cheap race seats for the Cobalt (the factory seats have very little side bolster and fat me kept sliding out of the seat). I found my cheap race seats on Craigslist and they came with some sort of home-made half butchered slides. I butchered them further to jam them in the Cobalt and completed the butchering to get them crammed into the Fireturd.
The Cobalt factory seats clipped in the front and bolted in the rear. I figured if it was good enough for General Motors it was good enough for me, so I welded up a couple of clips and welded them to the floor, then fabbed tiny legs for the back of the seat frames and bolted them to the floor.