Search a little more...there are many many threads on this.
A GT takeoff system is a great way to go. That's how I did my setup, got the mufflers and drier-side mid-pipe, then took out the Y and fabbed up separate 45* bends to the mid-pipes. You can use your stock v6 pipe past the y, as it is 2.5" and the same size as a GT pipe. The rest of the piping before the Y is 2.25", which if you can get ahold of a GT h-pipe, you can weld the h-pipe to your stock piping past the cats.
If you insist on doing away with the cats, just get some downpipes made. You won't really gain anything from deleting the cats, as they flow very well.
Don't bother with long-tube headers, they don't do anything (again, search!).
Mike -- 2005 "The Beast" (Formerly a V6, now a forged/stroked 5.0L V8 sportn' a Kenne Bell 2.6L @18psi, and many mods
2006 4.0L w/Powerhouse turbo and TR-6060 :kooky: