Here's some good reading but keep in mind there are other choices out there. I checked two stock ports on a set of 440source heads on my bench and they were around 267 cfm. With a little work they are much better. https://board.moparts.org/ubbthreads/show...e=3#Post2885759

1970 Duster
Edelbrock headed 408
5.984@112.52
422 Indy headed small block
5.982@112.56 mph
9.42@138.27

Livin and lovin life one day at a time