OK, with distributor under #3 cylinder and mark "A12" it is either an imported used non-US 1974-up A12, or it might be an A12A. But b310gx says the engine he saw was definitely marked A12A. So assume it's an non-US A12.

In either case you will need to modify the motor mounts to put this engine in your Datsun 1200.

I wouldn't worry whether it's A12 or A12A about this unless you are talking about racing or boring the cylinders.

I'm using this engine in a Lotus 7a replica (locost 7) that I'm making from scratch. I wanted to use a better engine than the MG Midget 1275 I was going to use.. On of the guys from down under said the 1275 was Pommy! So I don't want to use a Pommy engine in my replica!

and again I really thank you for all the help you have given me.
dog

I am thinking about boring and using A14 pistons. The color of the engine block is blue and the head was silver in the picture. Do they paint the heads silver ? I'm use to British cars where they paint the engine and head the same color. Are Datsun heads alumunum(sp?)
Dog

Yep, heads are aluminum. The A-engine is a very reliable engine, and might not even leak any oil ...

My A12A is imported from Japan and it has oval ports head with manifolds similar to early 80