Aussie MGB Build Date

[Michael Baxter]

Hi to all, I understand that this subject has been probably done to death but was hoping someone could give me a definitive answer or point me in the right direction to find the accurate build date and other relevant dates for a very early MGB which was first registered in Australia in late January 1964. From the plate on the vehicle are the following numbers:
TYPE YGHN3
CAR NO. 21131 (then a space and the further numbers) 967
ENGINE NO. 18GUH22641
COLOUR