Yeah I think you’re right about it being a busted helicoil. I bought it off eBay but it makes me think that the seller out this in to get it to thread, or it was fitted as standard and busted on removalThe thread will be a standard M12 thread, Ford haven't changed that for years.
The supplied spring is a real odd one? I have no idea why they would supply you with a spring? Just for my sanity could you post a pic of the spring too?