usually they come in a set of 4, the fronts being 6", and the rears being 8", obviously a 8" wheel is going to foul on the rear if its slammed. ( Coilovers being the give away for you mate)
It is possible for the rears to be fitted with spacers on but then you will need to completely roll the outer lip of the rear arch out of the way pretty much so it is sealed on the inside of the arch. I think the offsets might cause a bit of bother aswell, but i might be wrong on that one.