hey iceman, i too have a 99 cobra that is lowered 1 and a half inches with hypercoil springs, and even 255/40/17 will rub just barely when all the way turning. just to let you know, on the 99's the sway bar just barely misses the side wall of the tire when sharp turning. just remember its not the tire height that will most likely cause the problem, its the width. I tried 275/40/17 up front, and luved it, until you had to turn in a parking lot haha, good luck
the 03/04 cobras seem to have more room up front for wider rubber. the thing to do is keep as close to stock width up front as you can. the potenzas so3 tires seem to be wider than normal even on a 255 width. bfg is the way to go if you can.