With the grouping tool you could also "make new group" named "head" and the select "all" for that group and then spawn the head as a prop... the materials should stay intact. I had changed the .pp2 to .cr2 to get Morph Manager to transfer head morphs to a head prop in the past but have not tried it lately.

You could also export the head posed with different morphs applied as seperate .obj and if you have not moved the head in space you can then import those as morphs to your new prop and that can move and morph but if you moved the head prior to exporting the morph .obj files then as morphs those will also shift the head prop around in space.

Just FYI if you have some different objects that you want to move as a group you can parent the together... in this case open the hiearchy menu and drag the lips, eye, whatever onto the head prop and they will move and scale linked to that head prop as a parent... you can fuse parts together by exporting them as a single .obj and importing back in but youy want to make sure their are no unintended conflicts in the materials assignments.

The easies way to cap the neck would be to shape a ball or cylinder prop to fit in the neck and parent that to the head prop... if you cap the neck by altering the geometry it won't take the morphs any longer.