iron heads for a 408?

I figured they arent cheap...lol. I'd be interested to see how they do arrive at the numbers they do. Like what inputs, and how involved are the data entry tables. Like I said, that 198cc port flowing 315 cfm at 28" is maybe doable in a DOHC import.. not a single valve, snakey shaped pushrod V8 configuration. I'd have to call to make sure my memory is good enough, but I think a friend has gotten 330ish on Boxer Subaru heads (WRX), but those ports are only 1/2 as long as a typical V8, shaped perfectly, and have two intake valves worth of area.