I have 98 TAHOE and a year ago I replaced my entire exhaust with stuff from summit racing. I looked extensively for a true dual set up, but the gas tank presents a problem on the drivers side because it is in the way of running pipe straight back and I did not want a dual setup that ran down the passenger side then crosses over to the drivers side because I wanted my exhaust length for both sides to be the same.
My final decision was to run JBA stainless headers, new magnaflo cat assembly and a flowmaster muffler assembly. I chose all of these parts because they could be bolted on by me in my garage with no modifications. the cats were a dual assembly with a flange that bolted directly to the flowmaster muffler. The flowmaster is a single outlet setup.
Hope this helps