predator heads
Aren't they the Brewer heads? I know a little about them, got some info and pics when they first started. As I recall they based the idea off of the fact that BB Chryslers and AMC engines only had a .040 bore spacing difference so they figured they could make one basic head that would work on both blocks with proper machining for each.
They supposedly flow huge amounts of air but one head porter I know is of the opinion that they got those numbers without a valve in the port. I don't know if he has any experience with them though. I know I don't but they sure look impressive and Eric Shelton was using them for a long time to run some pretty stout numbers.