Best headers for duals set up
What mufflers you pick depends on how you want the system done. If you want duals to the rear bumper, you've got a lot more selection since you can run larger mufflers in the back, where the stock one was. Flowmaster single-chambers (I think they actually call them resonators on Summit) seem to be a popular choice for a good sound without being too loud. Bullet-style mufflers are also going to be quieter routed out the back compared to being dumped; Dynomax Bullets, Sweet Thunders, and Spiral Flows are all popular (I think the Sweet Thunders have a necked-down inner diameter compared to the inlet/outlet size; something to keep in mind), and Powersticks sound great, too.
Any header that Element listed would work just fine. Pacesetters are very commonly used.
I have LPP long tubes and x-pipe, all 3" true dual, bolted right up.

