No, you do not need to extend them.
I had to UNBOLT the "L" shaped hanger that holds it close to the frame though. It would tighten up too much at full lock.
I have a few concerns with mine, which I'm still trying to work out...when I go full lock, I lose brake pressure, the caliper hits the a-arm. When I did stevens truck (DCVRP) he had these cool little triangle thigns that bolt on the bottom of the a-arm that are new bump stops...thats what I need and I can't find em! I'd highly reccomend putting those on when you install. They are from fabtech, if you don't have them already.
Also just make sure your joints are good when you do it, if your ball joints are bad you are just polihing a turd...hate to say it but the lift spindle exacerbate any problems you have...when I did mine my upper right was bad...after I bolted it up and took it around it was acting up and wouldn't align...took me a day to figure that out :)
08 Cummins Mega Cab, 7" on 37
02 Explorer Sport
08 Brute 750 on 29.5