How to reasign skeletal mesh to a different skeleton?

Hello everyone, I’ve been having quite a bit of trouble reassigning the skeletons to some of the skeletal meshes.

These are all meshes from the marketplace that have the Unreal Engine skeleton and I can retarget animations in between them both with no problem. However if I want them to share a single skeleton in between them they look messed up. Is there something I’m missing about reassigning skeletal meshes?