DO IT ! If your not wanting any drone ..
My setup: 04 SSS h/c Radix'd Lq9 Pacesetter LT's Dual 3" to single 4" Magnaflow deisel catback.The og muffler was a 30" , I added a 12" long bullet,still to loud and alot of drone.I finally added another round 16" Magnaflow after the axle (spare tire locaton) and it still was LAF and droned.
Notes..no cats 2 mufflers , 1 resonator=loud/drone..
Get a 4" diesel Corsa or newer 6.2 oem muffler and drive headache free! the end...

 

I cut one open not long ago, not a great flowing muffler but it does support 400 oe hp.
I ran my arh's and the oe muffler without the resonator for a month before I put the m/flow on.
Oe baffles rattled, muffler sounded like a flowmaster. thinny, buzzy

 

Yeah, that doesn't sound good at all. I'm beginning to think that finding a straight through muffler to meet my goals is going to be near impossible. I think I'll go hit up some good exhaust shops around here and see what they have to offer.

 

i am running 4 mufflers...

dual 3" with 2 right after the xpipe and two more right before the bumper...

they are 16" CGS mufflers.

still a bit loud without cats.

 

i was running the 36" 7" round magnaflow, and it was pretty good, sounded like a diesel. its straight through, not baffeled.

I changed my exhaust a month or so ago to use 2x 6" round 14" magnaflows, and one 5x11x22 magnaflow. dual 3" to single 4"

http://www.youtube.com/watch?v=i98EB4PzKS8

 

I haven't looked at them for a while, so I don't know if they still sell them, but you might check out an Edelbrock RPM muffler. I haven't heard one on a V8 but I had one on my 94 Sonoma with the Vortec 4.3 and it sounded good. It's essentially a straight-through muffler but the path splits into 2 paths inside the muffler and then comes back together (you can still see through the muffler).

 

I run a 3" corsa exhaust and added a mangnaflow 11249(4"x9"x18") in front of the corsa muffler. The whole exhaust is straight through, no drone, and still sounds good under acceleration!

 

Did this on my Avalanche and it ended up being quieter than stock - couldn't even hear it running unless you had your head down by the exhaust pipe.

 

I ran two flowcrappers on my old truck. I liked it for what it was. I didn't have headers on it so it wasn't much to speak of. Even for Flowmasters it didn't drone hardly at all.

 

This is what I had to do to keep the strait thru performance and cut down on the drone and it worked ,and sounds really good, nice and deep and still loud at WOT.
Here is some videos:
Start up and Idle.
(http://www.youtube.com/watch?v=A9SWc0Sx1Lo)
Start up and rev.
(http://www.youtube.com/watch?v=QDkuqRRXVUA)