If this is going to keep you awake at night do yourself a favor and measure the head bolt. Now measure the head and the depth of the hole. See if there is anyway that you can use a longer bolt OR STUD to see if you can get down deep enough to hit the good threads at the bottom. Like I said earlier when you start a new build one of the first steps that you do is to chase the threads and thread the hole the whole way down to the bottom. That way you get proper torque on the bolt instead of trying to tap the hole with the bolt. Maybe your builder skipped that step, maybe he didn't. This is why I build my own engine so there is no second guessing. I know its done right. To many shoemakers out there. If you need a longer bolt check Summites site and buy a single LONGER bolt for that hole.