The recommended compression ratio for a camshaft like that using A12GX induction is:
* for use with regular grade gasoline: 10.0:1
* for use with premium grade fuel: 9.0:1

Now the cam grinder may have his own recommendation. There is no exact science here.

You should be able to use the 9.0:1 with regular gasoline in just about any country. The aluminum head allows about 0.5 extra ratio over a similar cast iron head.