You have several options, the xr4i(2.8) had 260mm front discs, as did the xr4x4 etc, the 2wd cossie 4 pots at 283mm fit under 15" wheels as they had 15" as standard.
You can use the cossie 2wd discs/calipers simply by tapping out the existing lug hole in the hub, it's already the right size for tapping as well, this is very commonly done.
tabetha