I know that there is a lot of exhaust questions on here, about what sounds good, loudness and etc... I have a 03 1500HD crew cab, I scheduled to have my exhaust put on thursday. I am having Flowmaster 50 series mufflers installed. I will let you what I think. I was going to go with 40 series, but I heard a truck identical to mine with that series, and it was to loud for my liking.