Check out Mac LT Headers. You'll need an off road X/H pipe for LT headers. Mac Makes a Prochamber which works with their LT headers. In the next few months. I'm doing the Mac Catback, Ceramic LT headers, Prochamber, Hi Flo Cats(Need to be Street Legal)
I bet with an H-pipe and some good mufflers or resonators it would sound a lot better. Part of me wishes I'd held onto my Pacesetter L/T's and got an H-pipe and some Borla stingers or something. Oh well....
I bought the MAC headers from them and I had some problems. The metal flanges that go against the block were not flat and had to be ground down by a machine shop(I did not check them when I orginally put them in). The welds where the individual ehaust tubes collect were bad and had a hole develop. I was not happy.
Generally longtube headers sound like ass on the 4.0s and also cause extreme drone in the cabin. Not worth the small HP gain to put up with a car that sounds like ass and drives you nuts from the cabin noise.