Reply to "14” x 15” and 10” x 15” Gr4 wheels on factory GTS"

The Group IV wheels are 10" front and either 13" or 14" rear depending on which rear rim you have (they made both).  There is only one street legal tire available for this rim combo which is the Pirelli P7s which will cost you about $2800. for a set.  I have 10 and 13" wide Gotti's on my car and they are under fiberglass Group IV flares (riveted on per the way the factory did).  There is no way those rims would fit under a GTS flare.  You also have to cut the sheetmetal as the tires stick out very far and will hit in the corners when turning the wheels.  The Marvic rims are period correct in magnesium but you will have to cash in your 401K for a set.  A much cheaper alternative is to buy a set of cast Roin Group IV rims which they make to spec from the original wheels.  But again, you will have a wheel tire combo sticking out 4 " on the back and 3" in front.   Kinda like a Dukes of Hazard thing.  Hope it helps.