Not sure if it is any help at all, but on a disco and a rangie, the tow bar and jate rings use points like this:
they are a tube welded underneath the chassis with side plates, rather than through it. Even if it's not how it's done on yours, it would be fairly easy to make some if you needed. I had to replace the tubes on mine, as the bolts from the old tow bar were rusted in, and it wasn't a big job to do.
hope that helps a little bit?
Cheers
Mark