I'm thinking that the diff is exactly the same. Just the carrier is stronger, and yes, it's steel. The GV V6/Manual carrier is eye-dentical to the Sidekick carrier except for the hole you'll have to plug, where the air-actuator for the "shit-on-the-fly" passes through.
And for my part, instead of trying to fab up a "snout clamp" XL-7 style, I think I'll just refrain from dumping the clutch in reverse, which is what I did to break my aluminum carrier.