5/16 wrenching header bolts

The Hedman headers I have came with the 5/16-18 bolts with 3/8" hex. There are only a couple of bolts that I need to use an open end wrench on. I find that with the Hedmans any way that if I start those that are real close to the tube and hard to get at I start those first nd keep the header away from the head and bring the flange in with the bolt then do the others.