I have a 2012 GMC Sierra 1500 with 2.75" exhaust pipe. I am wanting to delete my muffler and add a glasspack without welding. Problem is, I can't find any adapters to fit anything. Do I go with a 3" or a 2.5" glasspack? And whichever one I go with, what size adapters/reducers do I use? The muffler shops in this area charge around $350 for this work, so that'* the reason for doing it myself. I appreciate any help given!!

You have to measure the pipe diameter after cut the muffler off. If its 2.75", then you purchase a muffler with a 2.75 inlet. This inlet should already be slightly enlarged to slip over your current exhaust pipe. Then use a compression clamp.

The problem with that is that there are no aftermarket mufflers that are 2.75" in diameter. They are either 2.5 or 3. That is where I'm running into the issue.

Go to summitracing.com and you can search for mufflers with a 2.75" inlet.

IMO, glasspacks tend to sound raspy/ricey on our V8'*.

First off, thank you so much for your advice. What do you think about the dynomax 17797 super turbo? I can get a great deal on it and it checks all the boxes. Let me know any opinions.

Can't say as I've heard them. But I do know Flowmaster Super 40'* are real popular.