The factory both is a 10.9,12mm bolt.It's not going to break.If you are concerned about it coming unthreaded then buy a new bolt and nut from ford.The nut is,like stated before,a ny-loc nut.If that still isn't enough for you put blue thread locker on it for more insurance.Just a heads up,if you have a DMD you will have to cut out the front bolt on the pass. side also.If you want to replace the nuts and bolts shoot me a PM I work at a ford dealer,and I purchased all 4 of the bolts and nuts when I replaced my control arms.
