p3 and p4 characters use different geometry, so a morph made for a p4 characer will not work on a p3 character and vise versa. There may be a way to change that, but i have never seen it. You'd have to find some P3 morphs. And if your question is do those exist, then your answer is yes. I believe the models at the 3d Comic Collective have a very large variety or morphs attached to them that can indeed be moved onto the centaur with morphmanager.