Yes, what I did was chop off M3's head and pop it on V3, so it's still M3 and it takes M3's morphs.

I'm not sure that Injection Pose Builder is what you need. If I remember correctly it works with only Daz morphs, -- it doesn't create new deltas.  

If the head your created is made from a series of existing morphs dials, you can save those settings as a POSE. Then use UMT to convert each of the morphs that are dialed to a new figure. Then load the new figure in the scene, inject your converted morphs, then hit your POSE to set the morphs.

If your Head morph is a custom morph or a spawned morph, then you need to create an Injection pose of it. Convert the custom injection to a new figure via UMT.

Make sense?

If all you want is custom morph on a new figure, than it's much better to convert the morph than use a Frankenstein figure, imho.