when i bought my k30 someone got rid of the bench and welded in some kinda crappy cloth seats, they were all tore up and hard as a rock.
body shop next door to the place i worked had some seats sitting in a new wrecked volvo they were stripping for parts, didnt need the seats so they let me have them.
2009 volvo seats, with 8 position memory.... only thing i didnt hook up, which would have been nice, was the heated seats. the buttons for that were on the dash or door. think i spent about 2 days getting them mounted on the floor and about another day figuring out the 50 wires per seat.
so needless to say you can pretty much put any kinda seat in these things as long as you dont mind wasting days of your time fabbing up mounts