If they are stock... 275s in the rear are fine... hmm... probably 35 profile as it will give you a slightly taller gear, increase your gas milage and keep you from spinning them as much.

Caution: It WILL make you seem like you are going slower than you actually are. So for a 65 mph speed limit... do 62.

If you have aftermarket rims... well... I like my tire choices...
(see the picture to the right in my signature) Front: 245/35R18s ... Rear: 295/30R19s