if the truck is lifted, do you need a longer or shorter track-bar?
mine has the leveling kit, should I just get an adjustable one?
I want the strongest they make, who makes the best?

 

Longer, adjustable is your best bet, and Don Thuren, hands down.
http://www.thurenfabrication.com/

 

I have Don's adjustable track bar on mine, and it's a really nice piece. Less expensive than most of the alternatives, and certainly less expensive than any that are anywhere near as well-made. When I bought mine he was running about two weeks out on them, so it might take a while to get it, but worth the wait.