Help identifying my muffler

I have 2001 4runner LTD 3.6l 4x4.

The muffler that is currently mounted does not match what "the book" says it should. I suspect there is bolt in replacement but I can't figure out which one it is. In addition to what you can see in this pic, there is an O2 sensor up close to the cat, but its not visible from this angle.

Does anyone recognize this model? Or is their anything I should measure or look at to narrow down the options. It seems crazy to get a custom muffler when there is one out there that will bolt in!

Thanks,
Rod.

 

I replaced my muffler and pipe to 3 inch stainless with magna flow tailpipe sounds ausom runs a lot better. Make sure you go to a good shop to have it done. Good luck.

 

Just by the flanges it looks pretty stock to me.

 

My car seems to have a few oddball parts. It was rebuilt status when I bought it so I guess some substitutions where made when that happened. I eventually figured out that a Tundra muffler is the bolt in replacement part. Thanks for the suggestions.