unfortunately theres nothing around really with valve cuts to suit the compression height but there are flat top pistons you can play with. I would ask Peter Zekert as he gets stock every week and usually has good pistons SH for 80-200usd all depends.
You will be spending a fair bit to mod any other new piston unless you use a flat top with low enough comp height to miss valves and still get decent comp.

The best oversize flat tops I could muster are late isuzu Gemini fwd pistons 77-78mm for a safe build. Honda TRX 79 and 79.5mm pistons but flat top versions dont know what your build involves.

Choosing a piston with low deck height loses horsepower. The most HP will be achieved with a piston with only 0.50 to 0.75 mm clearance from the head. This provides quench will maximizes both HP and fuel economy, and reduces tendency to pre-detonate

For example, factory flattops with stock compression height and 0.6 mm head gasket. If using a high-lift cam, then simply notch the pistons which can be done with a hand-held grinder. You'll need to re-balance the engine anyways (whether the pistons are notched or not) so no worries.

The only time you want lowered compression height if is specifying ultra-low compression (e.g. 6:1 or 7:1) for forced induction. For the normal 8.5:1 or 9:1 compression by all means try to fit for proper quench. In 1977 Datsun changed their standard compression from large-dish with open chamber to large dish with closed chamber and it increased HP and fuel economy

going up in capacity through bore increases comp and shaved head also decreases the cc of the combustion chamber therefore its a balancing act that can allow lower comp height pistons due to high comp.

Daily or Franken engine. ... choose one

Going over the top and throwing fists full of money at a daily really kills the joy

Build a cheap and cheerful datto with the stock internal a15 and some nice bolt ons and live the dream of a daily datto that's as quick as a modern 6cyl.

Or build a Franken engine and have a high maintenance weekender that's probably a little faster than a 6cyl at full revs and a pig in traffic

To me the a15 in a 1200 needs to be considered like a v8. It's a torque monster compared to the a12. You shift way earlier and it pulls in the next gear beautifully. This makes an awesome street driving experience, compared to ringing the neck off an a12 to 7000rpm to keep up with traffic. Don't do mods that will kill the bottom end torque of the a15. Just free up the higher rpm a bit so you can run out the gears a bit stronger.

That's my experience anyway. I have had just about every combo you can imagine on road and race. Come round and drive my a15 coupe if you like.

I agree best not to go over the top with an A15 hence a re-ring, bearing, some comp and other simple mods is all you need. If you are wanting to go bigger capacity 77-78 is safe as 79mm is a little risky these days with the age of these engines. My basic prepped almost stock A12 in my last VB10 (higher comp, electric ignition, A10 carb, A10 fly) with worn 4 speed pulled a length to two lengths on a worked A15 in a vb10 repeatedly. The A15 had a 32/36, headers, e ignition and a few other tweaks but I think A series are easily unbalanced to run worse than factory as there are many things to consider when modding.
Also be careful with cam you dont have the vanette grind, Gx grind I found best on the street with twin SUs and even twin 40s suffered no low down issues with 10.25:1 comp, crisp revving all the way to 7.5k.

just got back from holidays,
wow,,,
thats why i love this forum.You ask a question and guys are super willing to help a fellow member!
Thanks for answering guys.i really appreciate it!

Zigmondo,
thanks for those contacts.i will pay them a visit this week.

beeontwenty,
thanks for the compliments mate.I honestly don't know the best security sytem for these cars.Do you have any ideas?
Too many cars being stolen of lately as i hear from friends on facebook.

D and ddgonzal,
i will research more on the advice you have given me.I really appreciate it guys.

Rallycar,
I've thought abit on what you advised.I will leave it stock for now with maybe just a 70 degree camshaft.
Another good thing for me anyways, is i will be able to see the difference in the future when i put on the a12t head and other mods on it in the future.
I have a soft spot for cars that are not too easy to drive.even as a daily.But point taken, won't go overboard for a daily.
I also wouldn't mind getting a ride in your a15 powered datto.

Cheers and thanks again guys