First rule of Poser morphing.  Never, ever start from an exported geometry. It will end in disaster.

Work from the original OBJ for the figure, LF2 in this case. Import the base OBJ into blender. Don't delete anything. If you can't see what your doing hide vertex groups (like the head). When you export the morphed OBJ be sure to preserve the groups. Someone who's more of a blender guru can help with the import export settings.