i know it's a straight swap for gti discs and pads on the mk2 but not sure about the mk3.
the diameter of the discs are 239mm for cl/gl and 256 or 280mm for gti.
solid discs are 12mm and vented are 20mm. try sneaking a look at some pads in halfrauds or somewhere to see it theres any difference. it don't tell you in haynes what the