I've got a 98 GMC K3500 4x4 (loaded) with 72K and have never had a problem. Super tow vehicle. (In fact its for sale now). Check out my homepage, photo album for pics. And, the only reason its for sale is because we dont need 2 large tow vehicles and the wife just got a 2500 Avalanche.
From what I remember they "fixed" any of the issues pre-1998 with injector pump stuff. But like I said this thing is the most reliable vehicle I've ever owned.