I would be a little careful reusing head bolts. The only true way to test if they are still OK, is to use a micrometer on the length. Its quite common for head bolts to stretch, and even if the thread looks OK by eye, if stretched enough they will give a false torque reading, and may even bottom out in the block. Its for this reason that a lot of engine manufacturers recommend getting new bolts.
Some engines (3.8-4.0 ford 6 cylinders, for example) actually get done up to a minimal torque setting, then turned an extra 90 deg as per the manual, and this almost deliberately stretches the bolt, so they can only be used once ever.