I can't say what the internal differences are, I just know that there's several aluminum/mag t-cases with chains driving the front shaft at all times.
Do your front springs have angle shims to point the pinion up? Mine do (4 inch lift) and the shaft holds up just as well as stock height. It drives fine even though it probably changed the castor from stock. My other Burb does not have the pinion angled up, but I can't say about shaft wear because I've only put 15-20K on it.