This is the range of the A12 stock cam though a more modern grind with more lift should help you get more airflow -- you've already got the ports for high-rpm flow.

Hopefully your double-springs will let you rev close to 7000 rpm (the stock A12 GX double spring were good to 6600). You should be able do it now. A new cam won't let you rev any higher, but should help with a little more power higher up.