Got the nut off, turns out that the socket I was using was not deep enough. I got a deeper 9/16, then tapped it down, then prayed, held my breath, bit my lip, and it came loose.

Now I have a small leak, coming up through the rear stud. I'm trying permatex, new gasket, and more of the technique above in hopes of avoiding having to remove the stud and reseal the threads. I'm afraid of breaking the stud, cause I suspect it will be rusted.

Any thoughts are welcome!