Hmmm ... i reckon the 510 is a fine car, and your mom may feel safer with such heavy sheet metal surrounding her ... but second-best for your own mother?

My mom drove a 1200 for a couple of years and enjoyed it. For some reason she now only wants full-size Ford or Chevy "dinosaur" cars.

So for an optimized utltra high-rpm race engine, the A14 sounds good.

For a typical street engine, the rod-stroke ratio in the A14 isn't going to overcome the 7% displacement advantage of the A15. The A15 makes more torque primarily because it's bigger, not only because it has a longer stroke (a bigger bore engine with same stroke would also have more torque, all else being equal (cam, manifolds, exhaust, etc).

A more interesting debate is the A12 vs. A12A (slightly bigger bore, but nearly the same displacement).

What is a sedan bar?

That's 'cause the orange wagon photo is of a PL510 (1600) rather than a B310. My mistake.

In the US the B310 was called the "210"; only the earlier ones 1974-1978 were called "B210".

There is a lot of information here on this part. Start with the Tech Section article Datsun A12GX Engine

GX exhaust manifold for sale

partial picture

Dems, what kind of car do you have? Your loom doesn't sound like a 1200.

The 1972 1200 had this wiring for the alternator:
A - White (connects to battery via main fuse)
F - White/Black (F on voltage regulator)
N - Yellow (N on voltage regulator)
E - Black (ground/earth)

The "A15" alternator you have may be an internal-regulator model with these marks:
A - main fuse
L - choke relay
S- connects to A
E - earth

The Nissan catalog lists an A14T. T = Twin (something). This is the twin carb engine.

My old Nissan catalogs show this:

Ball Joints
B110 - PN 40160-H1000
B210 - PN 40160-H1000 (1975 catalog)
B310 - PN 40160-H7400

Some interesting specs at Early US Datsun Engine Info

"standard" A14 come with different compression ratios:

8.2
8.5
8.9

The US engines got the 8.5 engine