I dis with Schwarttzy on this one. I think the crawler t-case is much more useful than a locker (especially if you run 35" tires). However, I would not mess with a swap unless your factory t-case has failed. Its one of those "if you're going to swap it...then might as well upgrade to the 4:1" type jobs. The performance gain is entirely in low-range, so you won't see any difference at all on the street.
On the rear locker...
The one that comes with the Adv. Pak is questionable at best. It uses round pins to engage it, and these tend to wear out in a fairly short time. I recently spoke with Eaton, and they have replaced the "pin" type engagement with a "dog-ring" type on the 8.6 GM axle. This is the type used on all of their other stuff...14-bolts, D-60s, D-44s, etc., and it doesn't wear-out as fast. So if you want to add an electric rear-locker...I would opt for the newer over-the-counter Eaton design over the stock AP locker. Of course, if you can pick-up a factory AP rear axle for cheap...then go for it. Just make sure you pull the diff apart and inspect the pins prior to installing it. You can get a re-build kit from Eaton that includes new pins.
Both designs are prone to crash-locking, and they ratchet themselves when you change direction from forward to reverse. Remember this when you're wheeling and be gentle on them. If you are a caveman wheeler and this is a concern...then you need to be using an ARB air-locker or an OX locker. Both of these lock and stay locked regardless of rotation changes.
