Instead of switching to one of these many glasspacks, why don't you just switch to one of Flowmaster's quiet mufflers? After looking at their website, it appears that most of their mufflers are actually pretty quiet. It's only those 40 series mufflers that are loud. Check out
Flowmaster, Inc The Muffler and Exhaust Technology Company manufacturer of performance exhaust systems, mufflers, exhaust kits and look up their 70 series muffler. From what I can tell, it should be almost stock-quiet on your truck, and apparently you won't sacrifice any performance at all.
I'm thinking of trying one of those 50s for my '97, since it also has a 40, and is pretty loud.