Hey guys, you're right, it is easier to just swap rear ends. if you can do that, I suggest that you do.
however, finding the perfect rear end, isn't always possible. if you have a 2wd truck, and find a 4wd truck...something gotta be cut and welded to make it fit into your truck anyway. or what if you have 3.92 and an LSD on a 98 axle, but you found an 03 w/ 3.55s and open? you have to decide, lose the LSD and the better gear ratio, or swap internals, or swap brakes.
what if you just spent $1000 on 4.56s, detroit true trac diff, and new bearings for your 9.25 2wd Dakota rear...then 6 months later find a cheap 8.25, with 3.55s and an open diff, with disc brakes on it...
what are ya gonna do then?
that's why I did what I did. I just had a killer rear end built for my truck, 9.25 axle with 4.56s, detroit true trac, rear end girdle, all new bearings in the whole thing, and had it sand blasted and painted while it was all apart. then came across a disc brake rear end from an 03 V6 4x4 truck. I sure as hell wasn't going to toss all the good parts I bought, to turn around and do an axle flip kit to the 4x4 8.25" axle...so I did the disc brake swap that you see here in this thread.
if you have a stock 98 9.25 w 3.55 open on your 4x4 and you happen to find an 03 9.25 w 3.55 open and disc brakes, our of a 4x4 then yea, swap the whole thing out--it's a bolt in deal. ....after you swap the yokes on the axle.