You will need custom caliper carriers making as i don't think the front calliper carriers fit the rear. I maybe wrong there though. Some people have fitted them to golfs so have look on VW sites i.e. uk-mkivs.net.
I am not sure why you would want to this other than for looks, you would need 334mm fronts (R32 brake discs) other wise you brake balance will be shot to hell. I have 256mm rears on mine.