Why not just use the 934 bolt-on flares that fit your model car?
I have seen many early cars updated to the 993 widebody look, but they were all done with a complete package-- fenders, bumpers, hood, decklid/spoilers, etc., to make everything fit properly and look integrated and correct. If you're only going to do the fenders to fit a larger wheel/tire package, why use the GT2 flares?
If you want to ask someone who is familiar with this subject, contact John Simone in Vista, CA. He has done several track conversions for himself, Clint Eager, Bob Erhman and others using the GT2, RSR and 993 widebody parts. PCA-SDR just had a tech session last month at his shop/home where he talked about the process.
TT