Really depends on how much drone you like. I have a 2009 Crew Cab Laramie, and started with the 18" Magnaflow kit by mufflex. Had it welded on. 3 months later had it cut out and replaced with a 22" Magnaflow. Still too much drone for my taste. Finally ended up with a Flowmaster 70 series Big Block II and love it. Took me three tries to get it right, but I'm happy.

All three mufflers sounded good at startup, but when on lengthy highway trips, the drone killed me with the magnaflows. Don't take this wrong, the Magnaflow is a quality piece, probably a better muffler than Flowmaster but their not for everyone. In a luxury truck like the Laramie, I want comfort with minimal sound inside with a cool mellow rumble outside. Mine is slightly louder than stock inside but a lot "meaner" than stock on the outside...

Good luck, may take you a few tries to perfect it.

 

I have the 18" mufflex set up and love it! my buddy put on the 14" mufflex and it sounds pretty decent too. I find the 14 has more of a bark to it, where the 18 is more of a growl. ha ha ha if that makes any sense!

 

At almost 70 with many truck behind me, I guess I can still learn. I have NEVER had a truck that I did not alter the exhaust system, and I can say I am truly startled at the observation on Flowmaster vs Magnaflow. This must reflect some new improvements at Flowmaster, as I have never been able to observe them (any model) having less drone in the cab than Magnaflow. I will say my grandson recently had one installed on a Silverado and I was surprised at the small amount of cab noise......sound like progress to me. I guess I should stop telling everyone NEVER buy Flowmaster, huh?