My apologies but what are you running Bob? I have 18x11 Apex rims and am currently running 315/18 BFG gforce R1Ss and they are even wider than A7 Hoosiers. Barely rub the rear sway bar, so popped in a 1/8 spacer in the back. Now, when I was running R7 Hoosiers I did not rub said sway bar and I am going back to Hoosiers this year since BFG and Toyo RRs are not being done in 315s
Buyer alert , especially for those running NASA, the above situation on Toyo Tires may impact changes you could be considering for your Mustang. There are benefits to using the Toyo Tires ( the point matrix allows some weight loss and maybe even a small HP gain ) but the larger tires are no longer available , so you will have to judge if you think the 305/18 will be a benefit or not since it is pretty well established they are not as quick as a Hoosier. BFG also yanked their 315s and they have nothing close now, so their perceived advantage for longer races 35-40 minutes is also gone.