This is New Old Stock Bursch - never installed or used, just have some shelf wear from sitting around.
Twin inlet style, nominally for 66-73 (or later years if you have backdated heaters or headers, obviously). This is the quieter version because it has the additional little resonators before the muffler.
Still has a really good, sporty sound to it.
These are NOT available in this exact style anymore, but the closest one still available new here on Pelican is$340 plus around $25 shipping.
I will take $260 plus shipping