BTW, are those bolts exposed on the backside. Mine are.
I once broke an exhaust stud off while changing the muffler on a VW Bug (a real one with the air cooled engine in back). An older guy I knew took a fucking hand drill and started with a small bit and worked his way up to the size just a red cunt hair smaller than the hole the stud was screwed into. At this point he peeled the threads out like a spiral on a notebook. There was not one nick in the aluminum and the threads were perfect! He had one steady hand to do that! God rest his soul! I miss you Jack!