Broken exhaust manifold bolts

Yup, what post #6 said. That's your best bet. Get a nut and place it on the head right over the hole and mig weld it to what's left of the stud. That one that's broken off deep is gonna be the trick. It's gonna be a challenge to build up weld without involving the threads in the cylinder head. Someone really good with a mig can do it. The drill bits and ease outs are a recipe for disaster there, IMO, as those studs are likely in there TIGHT. What will happen is, you will end up breaking a drill bit off in a stud OR breaking an ease out off in a stud. THEN you will have "fixed it so it caint be fixed" because drill bits and ease outs are WAY hard and will be all but impossible to drill out.