Quote - kind of like V3's basic eyes were.

This idea comes to mind. Load V3. Export each eye as a separate obj file. Load V4, turn visibility off for her head. Import the V3 eye objects, and position them exactly over the V4 eyes (scaling if necessary), and parent them to the respective V4 eye. Turn off visibility for the V4 eyes, and turn it back on for the head. Apply the same materials to the eye props as they had in v3.