4wd calipers and 2wd discs are fine you just need 4 washers to position the calipers and file off some of the inner caliper to clear the disc. its not hard
the other option is focus st170 caliper with there 300mm disc which goes straight on although i beleive the brake pipe need changing as they ar different and will leak.

or have a look at this chaps design, very good Price as well
https://passionford.com/forum/viewtopic.php?t=98183