If I recall the stud is welded to the plate. I think I drilled, tapped and loctited a stud in so I could use a stock style nut and look stock. No issues since.
Bringing up an old thread.. you tapped with a bigger size than the actual broken bolt right ?
Reference thread.
http://www.svtperformance.com/forums/showthread.php?625069-Solutions-for-broken-stud-for-hood-hinge