the one thing that you need to remember is that the HP ratings were measured differently, the A10 was measured "At the Flywheel" where as the A12, A13, A14, and A15 were measured at the rear wheels with all the accessories and emissions controlls hooked up and operating.
this is comparing apples to oranges.
in late 1970 the measuring standard was changed to the NET rating (as in at the rear wheels) by the SAE (Society of Automotive Engineers) to more accurately reflect actual available horsepower.
and yes this applies to all parts of the world for all manufacturers

there are 2 different A12 engines,
the first one has a bore of 73 mm. and a stroke of 70 mm. the displacement is 1171cc's, this is the one that was used in the B110 (1200) among others and made in the 1970's
the second one has a bore of 75 mm. and a stroke of 70 mm. (yes the cranks interchange) and displaces 1237cc's this one was made in the 1980's
the "S" designation is probably for a carburated designation.
when Nissan started to put fuel injection on different engines they began to use an "E" suffix to designate EFI and an"S" to designate a carburator
example: CA20S would be a CA20 with a carb, where as a CA20E would be a CA20 with EFI

it's a place to hook up an additional ground wire, IF you want to.
unless you really need an extra ground, don't worry about it.

as mentioned before, the vynal roof and the stripe were probably dealer installed accesories, as they were offered when the car was new.
the spoilers could have come from anywhere, including "Datsun Comp." (what is now called Nissan Motorsports) at one time they had a number of body parts available, unfortunatly they are no longer available.

OK, are you talking temp. in Ferinhite or Celcius? it makes a difference.
for those who use "F" water boils at 212 degrees, and for those who use "C" water boils at 100 degrees.
there are exceptions to this however, the main one being that if you pressurize the system, it will raise the boiling temp.
I can't give you all the metric equivilants to this , but you should be able to figure it out .
for every 1 pound of pressure increase, you raise the boiling temp 2 degrees. EXAMPLE; you have a 10 pound radiator cap on you car and it will increase the boiling temp. from 212 deg. to 232 deg.
don't worry if the temp. at normal operating temp reads over boiling unless it really is overheating.
not all OEM or aftermarket gauges are accurate, they will only give you a close idea.
this is why car manufacturers stopped putting temp. on the factory gauges. the best thing you could do would be to get a known accurate thermal measuring device and use it to check your coolant temp at normal operating temp. them you will know for sure what temp the engine is at when fully warmed up.

should work, but it would work better if you were to slot the holes and then use eccentric bolts for adjustment. they are those funny looking bolts that have flat washers welded to then off center. that way when you tighten them up the large flat washer on them helps hold everything tight. IF you are still confused about it go to a front end shop and ask them to show you what they look like.
as an alternitive, why not just put in a longer lower control arm? as I recall the 79-82 B310 ones will work and are about 10mm longer.

as of the 1968 model year, all cars and light trucks sold in the U.S. were/are required to have front and rear marker lights. amber in the front, and red at the rear. the idea is that this makes the vehicle more visable at night time. some manufacturers choose to make them also flash with the turn signals, while others don't.
in some states they have to be working in order to pass a yearly inspection, necessary to license the car.

check with your parts supplier to see if you can get them for a J13, this is the engine that was used in the 520 and 521 pickups, along with some of the 410 and 411 sedans, and some Nissan forklifts.
they were/are available in std., 0.5mm, 1.00mm, and 1.5mm oversize.
the bore diameter is the same, the distance from the top to the center of the pin is the same, the pin diamiter is the same, they even use the same rings . the only thing different is that the J series engines had a split small rod end that retained the pin with a bolt where as the A series pins were pressed into the rod, NO BIG DEAL. it won't affect the performance or durability at all.
the only thing you will need to check is valve to piston clearance, but then there is plenty of thickness in the piston head if you need to have them notched.
good luck.

plain and simple, blunt and to the point.......
how fast you want it to be will depend on how much money you can afford to spend, period.
there are no magic tricks, no secret ingrediants, and nothing that is really cheap that will help.
here in USAland they spend thousands of dollars to get a few extra horsepower.
sorry to say that the plain and simple truth is that how fast you want it to go will depend on how much you can afford.

when it comes to adding power it costs money. stop and think about it, the A12 is putting out almost 1 hp. per cu. in. sae. in other words 69 hp. out of 71.5 cu. in. that's a fairly good power to displacement ratio for an early 70's car. getting more than that is going to cost you some money. there are things that you can do to a stock motor that will help, but remember the old saying used by racers for years "there's no substitute for cubic inches".
the least expensive way to go is flat top pistons if you don't already have them, a higher lift camshaft, and raising the compression ratio by either changing the head or shaving the head you now have.
any way you go, it will cost something.