If you use a new nut, you are more than likely going to crush the crush sleeve more and that will lead to premature failure of your pinion bearings. You can mark and count the rotations needed to remove a pinion nut but ONLY IF you are reusing the same yoke or flange. If you install a new yoke or flange, it will not match up again. Unfortunately, unless you have an expensive inch pound torque wrench that can measure down to 5 inches or less to set things up properly, the best you can do is take a best guess and use some red loc-tite.