Sam's got it right, you can't do that.

All you can do is try to get a simular look using the other figures own morphs or create a new hybrid  of combined figures and you already know the limitations. The only real limitation would be the UV mapping of the two figures and if you have the time you could remap the UV's of the neck and head to match the body UV's or the other way Mape the body to the Heads figure UV's.

You can do that in UV Mapper. Not sure if you need pro version or if the classic / free version will do it. I only have the pro version. Really it's just a matter of importing the one map in the texture map layer and then opening the UV's of the other figure and moving the UV verts to match the map.