Max tire size for a 18x10 wheel for my 98 Cobra?

[svtcobralover]

Like the title states, what is the max size rear tire I can run on my 98 Cobra. I'm currently running 18x9's SVE Drift wheels all the way around but I'm about to order a pair of 18x 10's for the rear to get the staggered look. I was hoping to run a 305 out back. Is this possible with out any issues?

 

[cbrown9064]

My car is lowered and I run 315s on 17x0.5 rears. Needed to roll the fenders and beat on the inner wheel well on rh side a bit.