i highly doubt it would fit. the 5.4 has a taller deck height which should make the heads farther apart. even if the width is right i bet the coolant holes and whatnot don't line up, i have had seen intakes from different year non-PI 4.6s (not on mustangs) not line up right even though they are supposedly the same motors.
The 4.6L Cobra intake will definitely NOT fit a 5.4L DOHC. As someone else stated, the heads are farther apart on the 5.4L. Keep watching the TCCOA forums. There is an intake coming soon that will work with an Australian lower.