the barrel will need to be threaded/chambered to fit the action, you'll want a thicker recoil lug than the factory standard, maybe add fluting, a muzzle break, some type of finish such as cerakote or duracote.
I was just reading up and the 260 has a better ballistics rating than the 308... Or I was justing thinking about selling the 308 and buying a 338 AI AW