I suppose more info is needed. When you say "Super Six" with reference to 1960s slant sixes, you could be referring to someone installing a "Super Six" two barrel carburetor and manifold from a late 70s era vehicle or you could be referring to the "Super 225" which was another name for Plymouth 225 cubic inch slant sixes.

Is your motor a 65 motor with a two barrel carb and intake? Are there any other mods? Is it a complete later motor swapped into the Barracuda?

Slant sixes didn't come with two barrel carbs from the factory in 65, so you either have someone swapping in a later intake manifold and carb or a whole later motor. Slant sixes never came with factory dual exhaust, but you have several options to get there. Frankly, a single exhaust that is between 2 1/4 and 2 1/2 will flow plenty and weigh less than true dual exhaust. There is a small performance advantage to splitting the exhaust manifold into two groups of three (123 and 456) but it is perfectly fine to have the two pipes join back into one.