Everybody here gave good advice. The only thing I would like to add is Head gasket thickness.I don't claim to know it all but I do know this changes Compression ratio. Of course the easiest thing to do is put the larger combustion chamber heads and the thicker head gaskets then you don't have to disassemble the bottom end.If you already have it disassembled then I would check into milling the domes off.Hope this helps and good luck down under.
