BOZ said:It should definitely have all the special abilities and attacks of a displacer beast when it changes form. It would also gain the displacer’s speed, reach, and any skill bonuses.
For physical ability scores, as posted by wippit, they could be: Str 26, Dex 13, Con 20
Staying the same: HD, natural armor, type and subtype, base attack and saves, skill ranks, feats.