Thought I would give an update. I talked to two local exhaust shops today and they both listened to the truck. Both stated pretty much the same as the guys here... Converters.

The first guy said its very common and that the inner liner burns out and they start to rattle, But he wasn't completely sure on my cats, but thought the muffler was rattling on the inside. He said pull the muffler and then check cats.

The second guy said replace it all. Cats and muffler are both loose on the inside. He said they have had trucks come in that sound like a rod is going to come out the block and its just bad cats.

I had said earlier that I would start with the exhaust because it would be an "easy fix" WOW I had no idea how expensive this would be and the lack of available exhaust parts for the V10 trucks