Will Nyman

So I just got a 2013 Mustang GT, it doesn't have the track pack and is currently running the stock 18" Rims. I just bought a set of 20" FR500 rims for it but I'm getting conflicting stories about what tires will fit. Some say you can get 315s on the rear some say they rub. The front rims are 20x8.5 with a +30mm Offset my plan was to run Nitto 255-35 r20s tires on those. The rears are 20x10 with a +45mm Offset and I wanted to run Nitto 295-30 r20s on those. Will 295 be to much tire. The last thing I want is rubbing. Coming from my 1995 GT to a 2013 has been awesome. It rides nice and I don't want to compromise a lot of ride quality just to have a huge rear tire. Its also on stock suspension but I want to lower it 1.5" with Ford Racing Springs.