The Netherworks:
Vic3's head/Vic2's body
Stephanie's head/Posette's body
Vic3's head/Posette's body

shadowcat is developing a Vic2 head/MayaDoll body hybrid.

Dave has a Mike 2 head/Victoria 3 body hybrid in Free Stuff. He also developed a Victoria 2/Victoria 3 hybrid with specs2 and Wyrmmaster, but I don't know what became of it.

And Yamato has a tutorial explaining how to attach Tenten's head (Victoria 2) to Victoria 3's body, which you might find useful.