The thread does look pretty average. Are they all like that?
From memory, I had one of the threaded rods unscrew during disassembly because the nut was locked on.
So they should not be in the body that tight, and you should be able to unscrew them and replace them.
They are imperial, not metric. And M8 sounds too big if it was. (Ha ha.....as above...)
I sourced the mounting nuts from rare spares....Tail Lamp To Body Nuts LC - LX HK - HG All HJ - HZ Sedan
From memory they are not thin enough to use to assemble the body, but they would be a good start to working out the thread.
I’ll see if I can find pictures.......I hate to say it, but I might even have some nuts somewhere, but I just packed up the house to move in two weeks.
I find the bolt shops a bit hit and miss......some are not that great at identifying threads.
Edited by Lc69, 06 November 2018 - 08:51 PM.