That must be the case now. I got mine about a tear and a half ago. Sorry. Maybe if you get in touch with Waldron directly they can tell you which muffler they use. There was no name on them but they are stainless steel
If you do not plan to keep that engine just have them put a generic turbo muffler with 2" pipe to the muffler and 2 1/4" or 2 1/2" tailpipe. They can put it where the V8 muffler goes. I paid $200 to have that done before I got the header and dual exhaust. If you don't plan to keep the six don't spend too much on it now.
No difference. Just fight the urge to go too big. The pipe sizes I gave before sounded really good, especially at idle. You won't get a noticeable increase in power just from the muffler with this engine anyway.