Exhaust Help

I didn't know where to put this so move it if need be. I need help on what muffler to put on my tow truck. I hate to say it but it's a Chevy 6.0. I don't want to try a Chevy board it would be a pain in the *** for a muffler. The truck has true duals back to a single two in one out muffler the size of a 55 gallon drum. I am wondering if I should duel it all the way out or go two in, one out cat back. I dont want it to loud. But I would like a good sound. My biggest consern is cab noise and something high pitched. I was thinking about dualing it with Dynomax ovals. Or putting on one or two flowmasters. But Flowmaster makes like 7 types now and I dont know which one. Do you all mind helping?