Apparently wedge engines can efficiently work up around 9,500 rpm then you start to need to go canted valve to go higher rpms to finally hemi for max rpm.
It depends on the valve and port angle. I know actually making power at 8500 with a W2 or even the raised port W5 isn’t easy. Even on 340 inches. Guys claiming to run that rpm on OE heads with 400 inches either have no tach, a bad tach or they are bad liars.