thats the clearance between the wheel and suspension leg would need a spacer to clear the spring and platform I reckon.
And this is the work equips I ve got on the car at the moment 8.5x18 front and 9x18 rear just for an idea what they look like.
Im located in west sussex 10 miles from Gatwick
As for fitting straight onto a GTT I dont know, think these were previously fitted to a supra.
When I bolted one of the 10's onto the rear of the GTST there looked to be enough room for a 10mm spacer and have enough arch clearance, would have to probably be a stretched tyre to make it work without rubbing issues tho but hard to tell without havening a tyre on it.