I have a set of 285's on my 517, with 12:1 comprssion there's plenty of port velocity (very broad torque all over even with a big roller cam). I didn't measure the port x section all the way through but I saw no pinchpoints and the tall roof combined with a short turn is one of the nicest I've seen on any Mopar BB wedge.

The Chapmans are noted for being the most efficient of the MW heads (i.e., cfm per CC of port....380cfm is typically reserved for heads in the 325+ cc volume range but also you need to factor in that head (Like the indy) have the B/RB 'spacer' factored into the casting, tough to do a true Apples to Apples.....all I can say is the flow is outstanding