first you must run a 5 mm spacer in the front and roll all your fenders but you should be able to fit 275/35/18 on an 18x9.5 with a 30mm offset. i myseld am thinking about doing this but they only make these wheels in 350z fitment so time to save up for an sti hub swap ... heres an evo with the wheel size u would be running...
http://www.subydude.com/gallery/_detail.php?pic=1467

so you are looking at running a wheel with a 5mm spacer, that will stick out nearly 2" (28mm=~1.2", 1.5/2= 3/4", 1.2+3/4=1.95")more than stock with a 275 tire huh....that would be lots of fender rolling, and or camber, and or stiff suspension setup. good luck

thanks ill need it