As I found....just because the nut won't "turn" doesn't mean that it's tight (it could be frozen on the threads). While you have the car disassembled (making it easy to work on) I would loosen both nuts and lube them well. Then tighten them down "real good and tight" knowing that the threads are free to tighten down against the body. On my Barracuda, it was such a hassle to get a wrench on the nuts I didn't want to have to do it again for another 45 years..LOL!!!