I Need A12GX Head o anything Better,
may anybody have one?

Thanks.

Yes, the Nissan Competition head is better.

11041-H2302 GX CYLINDER HEAD (TO 6/73)
For use with any A-series engine built up to 6/73. It has 29cc combustion chamber, and due to its large intake port size, must be used with eitehr the GX or Mikuni/Solex intake manifold. Valve size is 35mm/1.38" (intake) and 29mm/1.14" (exhaust).
11041-H5703 GX CYLINDER HEAD (FROM 7/73)
Specifications are the same as 11041-H2302. For A-series engines built from 7/73.

99996-H1167 COMPETITION CYLINDER HEAD (TO 6/73)
This cylinder head is recommended for racing purposes only. Must be used with either the GX or Mikuni/Solex intake manifold. Competely ported, polished and fitted with competition intake (37mm/1.46") and exhaust (30mm/1.18") valves. For A-series engines built up to 6/73.
99996-H1165 COMPETITION CYLINDER HEAD (FROM 7/73)
Specifications are the same as 99996-H1167. For A-series engines built from 7/73.

None of these are currently available from Nissan. But you might find one used. Search the classifieds here for cylinder head.

Where are you located????

Thank, I'm in Dominican Republic.

amaury, have you seen the Tech Section article A-type Cylinder Heads?