problem with bir rims on a stag is offset and also width you need equal width all round no matter what size it is so no staggered offsets or widths also without pumping the guards the widest size you will be able to fit if you manage to get the offset right will be about 9 inches and even then depending on your suspension set up they still may rub.
if you are doing a kit it may have to be custom as there is not a lot still in production for the stagea