small block heads, 4027596 casting # any good??

I have most of the books written on head porting from the last twenty years or so. Most of them have been unopened as I get bored reading formulas and most of the math is over my head anyway. I came up with my own small block rule years ago without ever seeing anything written on the subject. 200cfm by .300 has been a rule I’ve used for years. After that check flow at every .050 to see the gains. I see guys listing their flow numbers to 1.000 lift daily even when their customer is going to run a .650 lift cam. We all have heard stories about how well some of the cars ran years ago with stock W2 heads. It’s not that W2 heads flow so well, but the fact they flow so well early at low lifts. Most guys aren’t running killer cams anyway so even that .650 flow number is nothing to brag about. But that .700 number does help the person. Doing the head porting if he knows how to use it.