Bone,
no the 6.9 only rarely experience cavitation; it was more common in the 7.3 version, and even more of a problem with the early powerstrocks.
With the exception of the small head bolts, they are bulletproof. I rebuilt mine at something around 300,000 miles just because. There was still cross hatch visible in the lower half of the cylinders.

Cavitation is when the cylinder WALLS are eroded; not the pistons.

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1982 300SD " Wotan" ..On the road as of Jan 8, 2007 with Historic Tags