Re: Aftermarket Headers
No one makes them. The only games in town are the stock (you have to modify them) SRT-8 headers, have a custom set built (like a couple of us have), or try using the stock LX log manifolds, which are substantially better than the stock WK logs. See this thread I did a while back: A better exhaust system for the 5.7 WK??
As to whether they work or not, with a good, "complete" system (tubular headers and a low restriction 3 in. system) you should easily pick up ~30-40 hp. I know it took about .4 seconds off my ET at the drags, and also improved the fuel economy. It is one of the two best mods. I've done to mine, the other being changing and advancing the cam.
05 LX/RT & 06 WK/GCO, modded similarly, MDS "ON" Light, Vortex Gens, Debadged, DashHawk, BT Catch Can, SRT CAI W/Add Air Inlet, K&N Filter, Sonnax Trans Press Booster, SC Tuner W/Adv Trans Tuning App, DS Tuner, Cust tube headers w/3 in. catback, Bilsteins, SRT frt/rear bumpers, Eibach SRT Lwr Sprgs & Sways, FRI Sidewinder Cam Adv 2*, 6.1 valvetrain, SLP 25% UD Pulley, BBK 90mm TB, SOS Coils/.060 plug gaps. 20 in. SRT Reps.