But it will eventually run 225/35R18, and probably Continental ContiSportContact3, depending on availability.
That is a big wheel and tyre for the 75!
Of course it will depend on the offset of the rims.
I've dummy assembled my Mazda RX7 mags with 225/50/16 tyre onto the adapter hubs I had made and that effectively gives the rims a +30 offset (+50 standard). With the 225/50, there is no way the front tyres clear the front edge of the side skirt with any more than about 1/4 turn on the steering wheel.
According to
http://www.miata.net/garage/tirecalc.html a 225/50/16 has a diameter of 631.4mm but the tape measure says more like 615mm.
The 205/40/17 I also have are said to be 595mm but measure 585.
The calculator says 614.7mm for 225/35R18.
Either way, the 225/50/16 I have measure 50mm larger in diameter than the standard spare wheel.
So if you have a tyre with a diameter more than, at a guess and it could be less, 600mm on a +30 offset, they won't fit in the front.
With less offset you may be able to use slightly larger diameter tyres.