I made a V3 morph for SP3's head. Here's how I did it (going from memory):

Load V3.
Export V3's head in OBJ format. Choose the "as morph target" option.
Remove V3, and load SP3.
Zero SP3 completely, and check that her hip and body are not translated or rotated.
Import the V3 head OBJ - uncheck all the options in the import dialogue.
Position the V3 head so that it covers SP3's head as accurately as possible, in particular so that the neck joints line up as closely as possible.
Export this newly positioned head again. Don't check the morph target option this time.
Apply that OBJ as a morph target to SP3's head.

If it doesn't work, let me know and I'll try to remember a bit better. :-)