The firewall is the same as used on the 850 and Cooper until mid 1965. The Floorpan matches a pudding stirrer that was later modified to take a remote shifter so that narrows it down to an 850. The holes in the drip rail are Aussie. So my guess is its an Aussie 850.
Now the issue I have is the aussie car number and aussie body number were located on the passenger side firewall until appox car 17000. (note passenger side for right hand drive) All I can think is that this was one of the very first Aussie bodies and they put the stampings on the drivers side briefly before going back to the passenger side. I can confirm Car 10942 and 10966 are both on the passenger side.
Car 10187 had a UK body number and Car 12178 has an Aussie body number so yours would have been one of the very first cars with an Aussie body number.
Here is a pic of a UK body number.
Attachment:
Example UK body number passenger side.jpg
Here is a pic of where the ID plate and chassis number were located on cars from approx 5700 to 17000. The body number is hidden under the ID plate.
Attachment:
YMA2S1 15700s ID plate and Chassis Number.jpg
Having the body number on the firewall means the radiator shroud was left blank so it doesn't matter that the radiator shroud is missing.
There is a chance the car number is also stamped under the passenger seat on the floor. Is there anything there?
Attachment:
Example of Passenger Floor chassis number .jpg