89dB is pretty much stock noise. My stock falcon ute has two centre/offset oval mufflers. Should be OK with 2x oval magnaflows or similar. The exhaust shop building your system will know for sure.

 

Thanks mate, I'm gonna go for the 2 oval mufflers just to be sure. Just had no base point to start from because I had an RD28 with no muffler or cat converter.

 

You'll want two or it will sound like a really loud wet fart.
Even with two mine was still loud, but that was due to making use of much of the old 3 inch exhaust.

 

Thanks for sharing, this is going to be super useful!