Now theres some good word from Brain about the heads. Personally, getting a head to go up from the advertised flow numbers, 40 cfm is a whole lotta work, never mind 40+ cfm. I have no idea about the finer points of porting heads to this level or the nature of the beast. I just read alot and take what I read about there flow with a grain of salt.
There flow bench said this, his sez that, another bench says there both full of it, etc...
The important thing about heads and the work done on them is;
the increase over the base line they took or know from there own bench on the work they did to it and;
A broad curve, not just a skyward ramp for launching rockets