This looks to be a direct factory replacement with 3-1/2" inlet/outlet. All shops I talked with claim the oem muffler has 2-1/2" tubing inside the case. I didn't have have a chance to speak directly with Pro-Flo because offices were closed by the time I got around to it so I cannot comment on interior tubing size but I suspect may be 3-3-1/2". It is advertised as a performance replacement for factory muffler with aluminized steel construction with a modest increase in sound. My intentions would be to replace oem muffler while keeping oem 3-1/2" stainless exhaust pipe, possibly with exception of also removing what looks to be a third catalytic converter just behind the factory Y-Pipe. I have seen the Flo-Pro #2510 advertised online for about $150 shipped. This muffler definetely will not save weight, it looks larger than oem behemoth....but if it adds any performance with a better sound and welds into factory system it is an easy upgrade. Please give me your comments and opinions, link posted below. Click on "part numbers" to see other configurations available...nice selection IMO.

FLO~PRO - Big Oval

 

Well from the looks of that Flo-Pro muffler and some pics posted of the factory 6.2 someone had cut open awhile back, they look the same. That Flo-Pro muffler would prob be a step up from say a 4.8/5.3 muffler but don't think you would see a gain from the 6.2 cat back. Only one way to find out, buy it and dyno the truck before and after. If you do buy the muffler post up some exhaust sound clips I would be interested in hearing how it sounds. I wanna say Flo-Pro is the muffler that H&S uses for there diesel DPF back and turbo back systems.

 

I missed the pics of factory 6.2 autopsy, going to search for it. If you Google Kinneys Muffler he has comprehensive media of this and many other mufflers/custom systems on his website with excellent soundclips. I don't know if they are site sponsor so I won't post a link.

 

Found the autopsy, thanks for the "heads up". That rules out factory replacement 3-1/2", may later consider true duals through another configuration of the muffler with twin 2-1/2" or 3" in x twin 2-1/2" or 3" out.

Like this 2011 GMC Denali 1500 6.2 Custom True Dual with Flo~Pro muffler by Kinney's. - YouTube

Autopsy below

https://www.performancetrucks.net/fo...9/#post4555859

 

I put the biggest magnaflow on I could find and it was a 3 1/2 in/out, I like it, could use alittle more sound but I have a feeling as soon as I put LT's on it will be perfect..