Here's an interesting dyno shootout 160 cfm head on a 306, 333 & 393.
What did the 550HP heads flow? J.Rob
He probably did this test years ago, but here's what they advertise now for AFR 205, the cam had .614/.621 lift.
205cc Street Head Flow Chart
......200.300.400.500.550.600.700.750
Int139,199,251,285,297,308,317,320
Exh121,170,206,219,227,230,232,234