I've just mounted the new engine in & the bolts that came out of the engine bar/chassis rails are dead. Too rusty to bother with. These are M8 standard looking nuts & bolts. Certainly not stock.
When I've looked for replacements, they appear to be M10 bolts, no nuts.

So do I take it that used to be encapsulated M10 nuts on the chassis rails & the bar bolted onto it from beneath? At some point someone has butchered these off & replaced with M8s?
Either way, what should be there? M8 or M10? I guess whatever used to be there, I'm using nuts & bolts from here on.
Are stainless steel ok to use for this job? I've some of those kicking about, but I'm always worried about them work hardening on more structural stuff.
Cheers
Chewie