Yeah there are "cat-back" kits out there, but on these trucks like he said all it amounts to is the final section behind the rear axle which isn't going to do anything for the truck.
There are a few companies who are apparently getting very close to having tunes available, and if a guy uses an "off road only" tune then you could do whatever you want to the exhaust and it won't matter at that point. But if you live in a state with emissions testing that's not an option.