u can actually use the 4x4 discs if you want,

when i bought my calipers i got 4x4 discs, they're only 278mm instead of 283mm, but if ya get em with them calipers mite as well use them up first.

only thing is you have to space the discs out more than the 2wd ones, (which can be a bit dodgey )

had mine on a year now and they're still ok