Mercedes License Plate Installation

I recently change plates on my 2002 Mercedes. The plates had never been changed (we buys tabs in Michigan). uch to my chagrin. Instead of plastic inserts to accept the bolts, Mercedes uses metal round plugs. Needless to say the bolts were rusted, the plug and bolt simply spun together in the trunk sheet metal. How can I easily remove the metal plugs & install plastic.

I would try a small hack saw or keyhole saw with metal cutting blade. Then deal with the aftermath.

I agree with jayhawkroy. That would have been my early suggestion but I held back a bit to see if anyone had anything more clever. Hacksaw it is.