Hate to disagree, but you can't fit 295's into the stock wheel tubs with the stock spring location. They'll stick out past the quarters, as it appears the ones on your car do. That's fine if you want to run with the rear end of the car jacked way up in the air, but not if you want to run at stock ride height or lower.
I run 295/35/18's on the back of my Duster on 18x10" rims. I have the springs offset a 1/2" in and the quarter lip trimmed back a 1/4", and its still tight. I only have about 3/8" to the springs, and no more than that to the quarters. Maybe less. Without the 1/2" spring offset, the tires would have to stick out past the quarter to clear the springs.
275's will fit just fine with the stock spring location, but we'll need to know how wide the axle is to give a decent guess on the backspacing.