Replacing body parts with props or conforming head figure is easiest, but need a lot of postworks. I'm more familiar with Wings modeling then with Photoshop and I prefer weld necks.

I've made NearMe with transplanted head of Koshini.
First I loaded both figures NearMe and Koshini. Hid NearMe head and Koshini body, both necks stayed visible. Koshini was scaled and translated to place head neck in suitable place. Exported visible body parts of both figures as an objects. In Wings I Cuted part of necks leaving up neck of Koshini and down from NearMe. I added some vertex and used bridge. Later I used slide edge to hide weld line.
I exported ready objects to geometries ans a Near_you.obj ;)
In cr2 file I changed obj names Near_me.obj  => Near_you.obj. With Cr2 editor I removed old head morph and copied Koshini morph to new head.

I think this way you can obtain better results then using props or conforming figures. You need a little practice with wings or another modeling software and some UV mapping, because  neck is not mapped. All morphs should works if you did not add any vertex in body or head. Unfortunatelly morphs do not work with neck, because it has new verts order.