best way to get header studs out

If the stud does break off (when it does it usually is pretty flush with the surface) you can always place a metal nut over the stud (even if it is slightly recessed in the head) and weld the stud and nut together through the nut hole. Then back the nut (now attached to the stud) out with a socket wrench.

The weld will bond to the nut and stud but not to the cast iron or aluminum heads. The heat transfer will also break the bond (rust) between the stud and the heads. I had a bolt that snapped off flush with the engine this weekend and it only took 30 seconds to get it out. Great method if you have a welder LOL.