Try this product from Ashland Muffler house its on ebay ( or make one yourself) ebay item number 252378459520. its a simple fix for a laborious problem.

 

sorry that's for a flange!

 

Sorry that's for a flange

 

Exhaust Manifold Stud Removal Tool Fit for Ford F150 F250 F350 4.6L 5.4L and V-10 engines 1997-2009

We bought this kit on Amazon for $35, it was worth every penny! 3 of the studs broke off 1/4 inch or so inside the right head. the guide guided the drill bit perfectly into the broken studs, easy - peasy! Although the extractor tool was a bit short on one of the studs, I had a set of exctrator bits that were deep enough to get the job done. A right hand drill is a must!!! We did not bugger-up any of the threads

 

I've never used a Helicoil, but from I've read about them over the years it's more of a "temporary fix" (and seem to be more of a light duty repair). I've used Time-Sert with great success! The cost is more, but a permanent repair! (80,000 miles on three blown out spark plugs - is my testament) They make many spark plug type repair kits, as well as other bolt type repairs. And their customer service is outstanding!
I did a spark plug insert on my sisters Honda odyssey - it was a mess evidently the previous owner (or their mechanic) cross threaded 1 of the spark plugs. It was so bad the standard kit didn't do the job, and I ended up having to use the Big-sert - everything's been good for over 10k miles. I looked at other similar kits on amazon and local parts stores (trying to save her some cash), but none seemed as complete as the Time-Sert brand. And let's face it - who wants to break down out on a highway a 100 miles from anywhere (or even across town).