Super Six HP gain?

So, the Slant Six in my '75 Duster(which is currently stock) generates 106 HP,(which isn't much) but I'm putting the Super Six setup on there sometime after the first, and I was curious if anyone knew how much HP I'd gain from doing this(I know I should probably upgrade to the 2 1/2 in. Exhaust as well) but I don't have the $$ for that yet.

And if anyone had any other info on how I could increase my HP(without the typical smart :bootysha: response of "put a V8 in it") I'd appriciate it.