Thanks for the advice. Asked about those ebay ones specifically. He said they're M16 not 5/8'. As an imperial newbie, as that nearly the same thing?
As for the "Don't go stainless" advice, i'm listening. Don't want to have to grind off, or worse have something fall off.
To put the question a different way, I have gone to almost every length to make sure that everything new that goes on it, won't rust. Where can I get nuts that will match the stainless elsewhere that won't go orange and crusty.