assuming you need area level of 120 for SU to drop, and certain boss (or maybe chest) added couple of level to the item they dropped, maybe it might be possible for SU to drop in terror.
random find from net:
For monster drops: ilvl = mlvl, always.
Use the area level list. Monster levels in Nightmare + Hell,
Regular: mlvl = Alvl
Champions*: mlvl = Alvl + 2
SuperUnique / Unique / Minion: mlvl = Alvl + 3
* Any species and type (Berserker, Fanatic etc.)
Bosses have predefined levels with no reference to area.
Hell Mephisto is level 87.
That was for normal cLoD.
Problem is, all level area are capped at 115 (at least from glance from couple of uber level / difficulty list) so technically you can only get up to ilvl 118 aka cant roll into SU quality (set is ilvl 100 i think?)