is there any stud sticking out?

if so you may be able to grab it with vice grips and twist it out.

if not then i would center punch the broken stud and drill it out very very carefully with a left hand drill small enough to miss your threads. then tap the hole clean and install new stud.

take your time and be very careful.

good luck

tom w

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.