Are you looking for Seph's battle models in the battle.lgp? If so, they are as follows:
Sephiroth (from the Kalm flashback): saaa
Sephiroth (from the final battle): muaa
In the char.lgp, he is in the following files:
Sephiroth (normal): bkhd
Sephiroth (holding a book): eoea
Sephiroth (holding Masamune): bbab
Sephiroth (holding Jenova's head and Masamune): bgjc
Think that's all. Hope it helps!