I'm a Machinist by trade, and saying something is "1/6" of an inch is unorthadox to me. The decimal number (.167) would just be listed as a three place decimal not a fraction. There are common fractions (1/64, 1/32, 1/16, 1/8, 1/4, 1/2) - this is refering to an inspected measurement. Are you sure you didn't mean 1/16 of an inch? 1/16'' is a good amount, but .167'' is A LOT, that's almost a "mile" in comparison to the tolerances given. You would have a ton of material banging in the cylinders, trying to find a way out, I dount they would be incenerated unless they've been slowly getting shorter since 04. Sorry for this lecture, I myself don't even use fractions except for tooling requirements.. I think of everything in decimal form.
How would this even happen? Pistol slap that bad all of a sudden? I've read head gasket issues with 6.0s, but that's not necessarily just with the 6.0s. Wouldn't this be a noticeable problem as it was occuring? It doesnt make sense that it would just show signs now if it was occuring over all this time, .167'' shorter and 3 years later. Maybe I read something wrong in this thread.
Best of luck though with the warranty work.