mods for the AU i6

[Paddyboy]

hey guys,
im looking at buying my dads au falcon classic.
its a 6 and its auto so it hasnt exactly got a lot of punch.
so what mods could i do to it for around 3-4 grand?
ive looked at jim mock and for 3 grand i can get around 140rwkw but they dont change the cam.
obviously exhaust and extractors is a must but i dont know to much about the AU i6 so any help would be apreciated.