I reused my head bolts.
The acceptable measurement length is in the FSM, my used bolts were as new spec wise.
When I reinstalled the head it was scary as Hell doing the final 90° tightening as I thought no way... they're gonna bust. That's how tight they got to go.
So, look up the measurement specifications of acceptable length and that will determine if you need to purchase new bolts. If they aren't perfect get new.