4.6L? 4.6? I don't need no stinkin' 4.6L! I got a 5.4L in my Mustang!
Seriosly, the 4.6 SOHC in the GT makes 260 HP and propels the GT to high 13 to low 14 second quarter mile times. And the 4.6 DOHC motor makes ~320 (01 Cobra), while the new '03 Cobra is making 390 (very conservative number). So, basically, Ford doesn't see a 'need' to up the displacement to 5.4.
I, on the otherhand, love 5.4's!
E