I had a similar situation on a 2.2 GM engine several years ago. I had a cracked head that I robbed the valves out of to rebuild another head. The machinist told me I should have just used the cracked head because it was in in overall better shape than the head I was building. He said that some of those between the valve cracks are a dry crack, and it will not cause issues. If your machinist will stand behind it, roll with it.