Muffler Question

I have a 73 Dart with a 318 I will be putting on Hooker headers and I am looking at the Jegs 2.5 in. exhaust system with Dynamax Super Turbo mufflers. What I don't know is which muffler to get there are so many different sizes and inlet and outlet locations. I know I want 2.5 in and out. If anyone knows which one I need, I would greatly appreciate that info.