I used PB blaster on the threads, ran the new nuts on and off a couple times.
Also used a steel brush to clean off all threads and around the studs.
Then I slobbered plenty of copper anti seize on each stud and in the nuts, then installed the gasket, sensor, and new flanged nuts. Do not...
The correct threads are 8mm x 1.25.
I use the Dorman p/n 982-008D from O'Reilly.
Use COPPER anti seize.
The nuts on mine nearly disappeared as well, but the anti seize preserved the threads underneath the nuts.