D.I.Y.
ok, I know all the retail dealers and installers out there would love to sell and install them for you but keep in mind, they're usually bolt on with u-bolts, and brackets, etc. which can be removed easily by someone hellbent on stealing them out of your truck if the chance came easy to them.
I prefer the welded solid approach like I did here, which would make them just about impossible to steal without destroying them to the point of not being able to use them again.
I also prefer Stainless to anything else, it's easy to weld up, never rusts, and will look good practically forever!
Here's a few pictures to give you an idea of what is in store if you so desire to take it on yourself.
I'm into these 6" polished stainless steel babies for about $350-$400 total. I used a 4" elbow under the bed and was going to make my own tee with a flow seperator plate into the 6" across the bed section because the preformed Teewas too expensive in stainless but found a used one laying around the shop which I promptly stole for this most important little project! The flow is just as good too... after all, you're taking 4" dia flow and dumping it into essetially 2- 6" dia pipes, no problems there.
They do get hot after a lot of 1000 degree exhaust rolls through but they cool off quite quickly. I have the cross tube spaced off the bed with a 1" square tube in two locations... and I keep the bed clean as well. You could put up a little garbage guard if you wanted to if you haul leaves and crap that burns easily.
Either way, don't let anyone talk you into 4" stacks, they look stupid (IMHO) but 6" is awesome if you have the truck to make them look good. A friend has 5" on his 2500 4x4 and they look almost as good as mine...
so, take a look and give it a shot. Keep them squared, just inside the bed cap rail and make all your connections square and tight. TIG welding is a plus.