Although the axle sticking out of rear swing arm might look as though it is not replacable; it is and often should be! While the swing arm will bend more often than the axle, it does happen. And if you spin your bearing on the axle it will also wear a grove that replacement is the only answer. AND if you are converting from wet to dry suspension then axle replacment could be an easy solution to the lower mounting of the rear shocks!
Note that the threads are different for each side of the car - use the axle with the standard threads on the right side of the car, and the axle with the "backwards" threads (turn left to tighten) on the left side of the car.