Needing to install a 3" glasspack on 2.75" exhaust. Can someone please give me some help with suggestions on a good way to get them clamped on? I don't want to make it permanent. 3" ID/OD don't fit, so I'm at a loss. And I'm told not to put the muffler over the pipe. Do I need to go smaller?

 

What year truck?

the stock muffler on my 05 was 2.75" in and 3" out IIRC

so i cut it out, welded on a 2.75" to 3" adapter, and welded my 3" in/out muffler in its place. the adapter plus muffler was the same length as the stock muffler so it fit like stock

I'd assume you could use clamps instead welding

 

Nothing is permanent take it to an exhaust shop.

I do all the work on my vehicles from paint/body, building engines, transmissions, gears etc.
The only thing I ever farm out is upholstery work and exhaust work...
IMO save yourself the headache and shoddy work results.