Just a tip for these headbolts: depending on how abused the engine was, they may be dirty. Like very dirty. Mine looked like they were packed with dirt. If they are this bad, you need to clean them out really well, and make sure that your head bolt bit fits all the way to the bottom of the bolt. If not, it will strip the head bolt. I did this to one of mine, and probably spent an hour trying to get it out.
If you have the misfortune of stripping one of these head bolts, go buy a 3/8 inch 12 point socket. Put it on your head bolt and hammer like hell. Did the trick for me, but the socket is never coming off.