Ok so iv found out a12 head fits on a15 good or bad I dunno what about a12 dizzy??

Yes it's well known that A12 head fits on an A15. There are some functional differences, but even the factory fitted round-port heads on some A15 engines.

Likewise the A12 dizzy fits and works well. All early A-series distributors interchange (A10 & A12), and all Late A-series interchange (A12, A14, A15, etc)

Cheers for that m8
Another stupid question the a15 stock with stock a12 head will go better then stock a12?

good question. Yes, A15 with A12 head will have more performance than A12 with A12 head. The reason is the increased displacment: "there's no substitute for cubic centimeters"

Haha I think you mean "there's no replacement for displacement"

Ok cool. I have a 1200 ute 1980 model will it bolt in I got confused with the wiki n a engine guy. And the owner of slug came and seen me today n told me that some one has swapped my diff for a sedan one. How long will it last with the a15/12 and another stupid question well really it's just to verify the a15 will bolt onto my a12 box. What did the a15 come out of?

A15 is out of the Nissan Vannete(a van)
The standard datsun a12 4 speed should mate up with not much drama.

Standard A12 gearbox will bolt up... but Nissan never fitted the small box to even an A14. There is a good chance it will break within a year. I have broken some myself that way.

Don't forget if fitting the early A12 head you need to make a modification to it. But later A12 heads fit on with no modification needed.

Hmmm what mod do u need to do? Mines a 80 model

A15s came out of several models.
In AUS out of the last of the B310 sunnys, but mostly out of Vanette.

If your head is a pre-1974, you need to drill/grind an oil passge. If it is post-1973, no worries just bolt and go.