As mentioned, the nut is tack welded at initial assembly.
Should be the same as the one on your 750. If not, take them both off, grind off the weld securing the nut on each one, dismantle and swap the good top link one to the other.
Make sure that you check the plastic bushes at the top and bottom of the tube and use the best ones. The shaft will be rusty, so give it and the inside of the tube, a good clean up and some lubrication which will not attack the plastic bushes.
Remember to resecure the nut, you could use a Nyloc or you could line drill and split pin, but if you do decide to weld, do not let it get hot enough to damage the bush.
The entire assy is secured with two nuts on to studs in the gearbox casing and is no problem to remove and replace.
Rgds.
