Plenty of TEA and AI 243 setups going 450+ to the wheels. I would call Tony if you have a unlimited budget...he will get you into the 480+ range but it won't be cheap.

 

There are two reasons for using .040 gaskets. One is to increase compression and the other is to get a tighter squish between the piston and the head. That forces the mixture into the combustion chamber and can help with knock. I'd also get the heads milled ~.020 to get a clean surface and bump the compression up more for HP