340 exhaust system

With that HP, you want to use 3" to 2.5" collector reducers and run a 2.5" pipes especially if the pipes are mandrel bent. That makes a huge difference as 2.5" mandrel has 50% more flow than 3" compression bent pipes that are used by local shops.

Depending on what type of driving you do and how long you want the system to last, you want to consider spending a bit extra for stainless.

As far as the mufflers, it's really a personal decision in your hp range. Any chambered muffler like the flowmaster or Pypes Street Pro or Violator are going to give you the most aggressive sound. Mufflers like Dynomax super turbo, Ultra Flow, Magnaflow and Pypes Race Pro are going to be a lot more quiet except at wide open throttle.