The tire size is width/heigh/wheel. Some 275's will fit, all depends on the height. A 275/65/18, especially the Duratrac, will require a lift. You'll need to lift the front 2.5-3", so to keep the vehicle level you'll want to raise the rear as well (not sure if it's technically required for fitment, but is for aesthetics). Even with a 3/2 lift, so minor trimming might be required with those tires (mainly moving the fender liner forward).
That's in stock form. I see you have Spidertrax, they'll definitely rub. You'll need to plan on moving the fender liner forward, removing front mud flaps, and possibly trimming the front bumper slightly (even with a 3/2 lift).