Most people get brackets made by Wedge Engineering. When I bought my Recaro Speed's, I got them with brackets and sliders from www.recaro-seats.com. They came with Wedge brackets and went in pretty easily. I did have to modify the passenger side bracket slightly with a Dremel, but it wasn't a big deal.
www.speedwaremotorsports.com also has brackets that they custom build, but I haven't had any experience with them.