Dejavu, mine looked identical to your's when it went at 156k miles also . There was no damage to any of the pistons, but it let go on number 4 in the same spot. Since you've got the head off, make sure to have it checked (as mentioned) for cracks and such. And if you have any broken exhaust studs, now would be a great time to take care of it . I had one broken one, so I decided to replace all 7 (2-3-2). Unfortunately the 1st stud broke off on me, but I was able to get them all out and replaced. Shouldn't be a problem for another 150k miles. Good luck on your rebuild. Mine just rolled over 171k miles. Take care.

- Jim