The barrel would be set back, one turn probably, and then a finish reamer until headspace was correct. Stock inletting may have to be "adjusted" slightly. And if your bolt is matched you wouldn't have a matching bolt #.
That's kinda putting the cart before the horse. The thing to do if one was intetnt on swapping bolts would be to check headspace with the new bolt in place. There are three possibilities: Headspace will be too little, it will be too great, or it will be just right.
If it is too little by not too much, you can set the headspace by truing the boltface. If it is short by too much then a reamer will be used.
If it is too long the cure depends on whether the barrel has sights or not. No sights, just trim the shoulders until headspace is correct. Sights, set barrel back a turn and ream.
Just right, count your blessings.
Me, for one small pock mark, I'd just continue to shoot it.
