Just use the GX springs, but brand new ones. They won't put as much stress on the rocker shaft assembly as the aftermarket performance springs.

i work at a engine recondition and i tested the sring, the outer are all the same but the iner are all different but i will just get a new set of gx sring
thanks for all ur help

Stock valve springs may allow revs to a certain point when everything is at factory spec,but when valves are refaced and seats recut then the installed height is greater than original.
This means less spring tension when the valve is seated and less tension when it goes over the cam lobe.
Result is every time you need to check installed height and as well springs will age and get softer if they are used.
There are no shortcuts to doing it properly for the best results,Ring someone like Comp cams or crower in the US or Ivan Tighe or Crow cams/Waggott cams etc in Australia to get the facts on what you have or need.
At the very least a good engine reconditioner will have a Rimac or similar valve spring tester to see if the springs are OK and to make sure they all match at different load points.
These are the facts you actually need to know to have the right result.

Those on eBay are Nissan springs.

* Stock A12 springs: Go up to about 7,000 RPM, but engine is redlined at a lower RPM
* Stock A12 GX springs, got up to about 8,000 RPM (maybe 8,500) but the GX engine is redlined much lower

The Nissan springs are good. BPro sells both the Nissan ones and other higher-RPM ones.

Given you have a gx head and twin carb, you probably want higher revs than 6000. If the springs you have now are gx they will be sweet, but otherwise you can get some here: ebay gx springs. It says in the description these should be good for upto 8500, probably around where you are aiming.

the standard valve springs should be fine for mild to moderate engine mods.
As DD said the stds are good for 6000rpm before they become unstable.

unless you plan to wring the neck of your engine, stds are fine

i am doing the motor my self and just tryin to work out the best thing to use?
so far i have a gx head, twin 40mm weber and a manifold, i have an a15 lined up.
thanks aidan

i was goin 2 drive it on the road i dont no yet but i dont want a standed motor i it to be a bit of fun lol

What do you use the car for?

I use Ishkederian double valve springs, but it is for a race car, top end revs is important for me.

I use the regular Nissan springs. They are guaranted for 6,000 RPMs.