you would need the calipers, the disks, the pads, and i think probably some longer flexi lines, most tend to use braided lines
also a larger master cylinder to reduce pedal travel.
if its just for a road car then i wouldnt bother with gti6 285mm brakes, some 266mm brakes of a 307hdi or similar will be plenty sufficient, these are what i have and are perfect when set up correctly.