That one should still work. When the K-member is tight, the threads closest to the head of the bolt will be engaging the nut inside the frame rail. You have bad threads on the upper part of the bolt because that section was sticking up through the nut and was exposed to the elements. You can chase the threads on the upper part of that bolt if you need to. All you need it to do is engage the nut. It won't be doing anything once the K-member is tight.