If you use the helicoil and have to do the drilling with a hand drill, use and old head gasket, slide it up the studs till its about three inches off of the head surface and put a 2x4 block under it in a couple spots to hold it there and use it for a guide to keep your drill perfectly straight, in other words pass the drill bit straight through the gasket and into the stripped hole. Do the same thing with the tap. Then everything will be nice & straight and will bolt up proper. Good luck, Hass
P.S. take a good look at the bottom couple of threads on the head studs, if they've been on this engine more than a year there's more than a good chance that the bottom couple of threads have been eaten away by the lake water. Put in a new set or you'll have several helicoils in the block before long. Nothing sucks worse than torquing the last stud and feeling it strip.

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