best way to get header studs out

I think I would almost want grade 5 in that application. Rather than break, they will twist first. The grade hardened studs are really brittle. They usually break first. Also, when you install them, coat the threads with red high temp permatex. This will do two important things. First of course, it will seal the threads from the water jacket so you won't get a coolant leak. Secondly, it will act like a lubricant if you ever need to back the studs out, they will come right out. Lastly, I use the red high temp permatex on ALL of the header bolts, not just the end studs. This will help assure they will all come back out again. Since they are next to exhaust posts, they have a nasty habit of siezing up sometimes.