Unless your building the engine yourself i would talk to your machinest/mechanic about what sort of power you want from your A series and the parts you will need to do this. Pistons/cam/head work etc.

You would be suprised how many performance parts are already available here in Aust and then go to places like this for things you can't find.
By this time you will have a much better understanding of prices too and what things are worth. this is when you see a bargin and snap it up fast.

Best of luck with that tuff A Series.