I have found numerous articles relating to this, and it they all seem to point out the same problem. The issue is that I have YET to find one with their links intact. They all talk about a service bulletin, or buying a very cheap part, and removing the plastic cowl up under the hood or whatever.

The problem is none of them explain this in detail without the use of pics, so I have no idea what they are talking about.

This stupid clunk is irritating... its bad enough my whole interior rattles. I drive an 01 2DR Jimmy btw, if that makes a difference in any way.

 

Have you checked the hood hinge washer? They're bad for going on these trucks..
Open your hood and hold on to either corner of it. Rock your hood back and forth and if it's the washer you'll hear the clunk.
It's a dealer only part (unfortunately) is a tiny washer that fits on your finger tip. It's aboaround 5-6$.

 

This might help:
Hood Hinge Rattle - TSB 01-08-63-001B