Just in case anyone stumbles across this post, I'll answer my own question. Turns out the rotor, caliper, and bracket are different, but RockAuto and other sites list them because they say that the other fits those without "special ride handling." Now, I'm not 100% on this, but I've never heard of any GXP that doesn't have these rear brakes, but you have to know what you're looking for.
Here's the correct caliper for upgrading your caliper:
https://www.rockauto.com/en/moreinfo...432258&jsn=444
And here's the base GT caliper and bracket:
https://www.rockauto.com/en/moreinfo...432258&jsn=456
Interestingly enough, the GXP caliper is actually cheaper than the stock (probably because the stock contains the parking mechanism internal rather than using the internal pads like GXPs and 97-03s).
Basically, If you're replacing your brake rotors, pads, and calipers, there's no reason not to go with these (unless of course you own a 04+)!
So in closing, sorry about the noob thread. Hopefully someone finds this information helpful, or at least amusing!
