If you have a cat, you really need a small one to get any sound. My daughter's 94 GMC had the factory single 3" exhaust still on the truck. She wanted some rumble so I got an 18" Magnaflow with 3" single in/dual 2.5"s out. I don't recall the case diameter but it is a very small muffler. But it was really mild with the cat, I was floored. It was so close to stock that most people wouldn't know it wasn't stock. You can look straight through them just like glass-packs but they are way more mellow. Choose carefully.
