I used a v3a3 hybrid for a project a few months ago, but I did it the hard way. Used Hex 1.2 and imported v3's head and a3's body, got the head scaled and located, then moved the edges fairly close. Then came the repetitive part of matching each edge vertice to corresponding vertice on the head.  Worked well enough for the project. Here's a quick poser render.

I'll have to try the morph thing, sounds a lot easier if it works well.