i haven't done it yet, but it sure seems to me you have to pull the carrier, smooth out the part of the housing where the seal rides in a non disco axle, (on either side of the carrier) and install the seal there. all the front axle seals i've replaced i've pulled the carrier. and once the shafts are out, the carrier unbolts anyways.
i'm under the impression you install the seal where an xj or tj has it now, just outside the pumpkin. is that right?