Returning to the question of when George first left for New Zealand, which as discussed earlier, appears to have been in 1866, I can return to the PROV "Index to Outward Passengers to Interstate, UK, NZ and Foreign Ports 1852-1908"
I don't know where George landed, but if I list the possible George or Mr Griffith/s who went to New Zealand in 1866 from Melbourne, I am left with:
Griffiths, ---, aged 38 Departed June 1866 via ship Alma for Hokitika
Griffiths, Geo, aged 30 Departed Dec 1866 via ship Otago for New Zealand
Neither of those are any good because I know that George was in Hokitika by March 1866, so I may have to look in 1865. However, searching for Griffith/s in 1865, there is no candidate for George leaving from Melbourne.