That's about the right year model for the piston skirt noise. GM had a huge issue with that. It is caused by pistons with short skirts rocking in the cylinder. GM's solution with later models was to coat the piston skirts. It was never considered a durability issue, just an annoyance. If I remember correctly, GM even extended the warranties on those trucks to try to appease the customers.
You might play around with different lubricants to see if they'll make the noise go away. Otherwise, I wouldn't worry about it.
We had an '04 Tahoe with a 4.8 that had the same noise.