Exhaust Stud Problem

While replacing my alternator, I decided it was time to fix the two broken exhaust studs as well. I got one drilled out and removed, but I couldnt get a good enough angle on the second and I ended up drilling into the threads that the stud screws in to. Well I decided one broken stud was better than two, so I left it and put the manifold back on. As I was tightening the nuts, two different studs came loose. Turns out they got too tight and pulled the threads right out of the hole. Now my question is, what should I do as far as tapping/threading a new hole. If I go too big then the manifold hole wont go over the stud, but I could possibly grind away some of the manifold hole to make it fit, correct? Basically, what would be the best way to go about threading new holes for 3 studs?

Helicoil. They are pretty damn expensive but they are the shit. Since you have 3 to do ita ok, but the kit is like $70 locally and for the one hole I needed to fix it wasnt worth it to me.

Perfect...thanks.