Loctite is the best. But, if you have room, tighten assembly, then cut
bolt off 1/8 - 1/4" beyond nut, then rather than peening the whole
thing over, just go to work with a center punch on the center of the
bolt. This will expand it enough to hold the nut on. Welding is the
second best method, a good spot weld and it isn't going anywhere, at
least not this side of reality. Nylock nuts are a great thing, but
highly over rated, one use and they're junk.