What are those screws called and who makes them?

I want something that grips with a bit more surface area. What can't be seen in the pics is that the rivets also deformed the sheet metal, so that area is now compromised. I want to drill out the damaged area and correct this issue but distributing the load over more area (less chance of pull through).

Something that just screws in to a thru-hole will only distribute the load through the material that comprises the difference in the major & minor thread diameters - which isn't a lot of area unless it's a large screw. I think the limiting factor here is the XK body which needs more support.

They're still on there solid, so i don't plan on tackling this until later this spring on the summer; so that gives me time to think about it.