I am seriously thinking about putting on a full ATS tranny. If I do then what else has to be done?? Does the rear-end have to be upgraded?? Can it handle the power/torque??

You don't need to worry about the rear end, Very few guys have been blowing those up around here. I think juice nuked one or two but it was the locker not the gears. We've got some seriously large rear diffs on these trucks. Good luck with the trans upgrade and have fun! :grd:

You definitely want to get some tie-rod sleeves from Super Diesel, and you might even want to think about buying his centerlink. The sleeves are a necessity, but the centerlink is probably optional unless you are going to get really crazy.

One plus to the centerlink is that your launches should be straighter with less toe-in of the front wheels.