Hey mate you will need to make it 347ci with a alloy head to make around 450
to 480hp.
The cost for all this will set you back around $14000+ GST to $15000+ GST
for a complete package.
This includes a Trickflow manifold all ready to slot into the car & set the
computer.
Let me know if you require any more information.

does this sound ok ?

apperently it should do 11s to 12s

Well horsepower is cheap, reliability is expensive. My 427 has cost that much so far, and a spanner hasnt been turned yet, if it is the stock block i would say it is a little expensive. If full aftermarket bits and pieces, looks about right. Also, s stock block wont live for long at that power output, so i would be going aftermarket anyway.
Cheers
Brett