how to achieve 600 to 650 hp sb 408?

Nokke said

the heads has been tested they flow 307 on 650 lift that guy that flowed them has all the numbers so i can them if want and show you? yes i use and adapter to the 1050. the piston is dished and i have filled it with liqiud and the result was 26cc and the heads cc was 62 the rockers are td machine 1,6 rockers and the block is line honed thanks from niklas

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With just a valve job/chamber cut, narrowing the valve guide boss and short turn work those heads should go 305cfm at .500 lift! It sounds like that's what's holding you back the most.
The srp 220157/157 pistons should only have 17cc dish...you may have measured wrong?
What's the chamber volume? Are you sure about your measurments??
When ported correctly, that head will have a large chamber...more like 68-71cc. So some milling would should have been done or they didn't open the chamber up any.

Cam is too small for that power level.