You can fit them and elongate the top hole like Ray says to allow the camber to be set correctly. The reason they are different if because the GTI ones have a deeper bracket to accommodate the wider track of the GTI. If you fit non-GTI coilovers and elongate the hole, the strut will be further angled away from vertical. This is a non-GTI Wietec coilover strut, compared with a standard GTI damper: