I would get the original diff rebuild and see how it goes. Don't underestimate it. They can take a little bit of punishment. And by the sound of it, you are going to keep the A12 which won't give as much torque as the A15 would.
The original A12 diff also has a very nice ratio.

Give us some more info on the setup. What are you guys going to do to the engine?
If she is going to use it for drag racing, what class is she going to compete in with the A12 sized engine?

By the way. I also have a stock standard A12GX. 1977 model and live in Bloemfontein.
Drop me a PM if you wanna chat private.
Regards

It was me who sold the aluminium tappet covers from South Africa.
Must say that unfortunately I searched the whole south africa for those that were sold in the past and there is no more to be found.

I would also give the thumbs up for carting over motocross when it comes to my child.
I would say that he has a better chance breaking a arm when riding his BMX bike like a maniac than racing a cart. They are very tight gripped on the road surface and will take a crazy move to make it fall over, if it even is possible. Find out the classes, maybe you can share one cart. He drives junior class and you drive senior class. Or something like that.

Always wanted to ask the following. I see in USA it is very common. How is it to live in a wood house? Here in south africa it is not heard of. We build all houses with bricks and cement. WHat I hate about it is that if your soil isn't right, they tend to crack at certain spots of the walls.
Is it not cold in a wood house? Sound proof?

My A12GX runs 110Km/h at 3500rpm and at 3800rpm it sits precisely on 120km/h

PM send

I will definately hang around here. At least once a day I check in here to read new posts.
Enjoy reading about the progress of other people's projects.

Thanks. You guys don't know how hard it is going to be to see someone else driving off with it when it is sold.

What do you mean "should take my own advice"
You also leaving the hobby?

Wish I could keep the car, but I need the cash.

Just to say goodbye to all my fellow datsun members. I have come to the sad decision to sell my 1977 Datsun 1200 GX. I just wish I lived in Aus to sell it to a member of this site to keep it in the family and also who will take good care of her.

Reason, need to buy a house and can do with the extra cash in the pocket for this.