You can fit XW to XF stubs, hubs and calipers, you will need to fit a bush on the outer tie rod end and shorten the tie rod. this is the cheapeast but tend to cause bumbe steer and reduces steering lock.
Places like CRS can supply kits to fit discs and calipers to original stub axles, this does not change steering or ride at all but is more expensive check out the link below, you will need to source discs and calipers as per there recommendation
http://www.rodshop.com.au/brakekits/brakekits.htm