first off i believe that the stroke of the 3.0 is the same as on the 2.5 the bore is the larger factor. second there are things like rod ration when i comes to seting up a car for high rpm operation. the duratec lower end is probably good till about 8,000 beyond that the rods are too weak and the crank to heavy custom parts would be needed i personally dont know about the valvetrain terry will know best in that department also you have to have the flow potential to spin the motor that fast whats the point of spinning that fast if the air cant get in/out quick enough. also i know shift at around 6800 and my car drops to about 4800 when i shift so with a 8000 rpm shift im thinking 5900 or so would be where are motor would land. so far the intake hasent been the limiting factor on out motors there are many 3.0 floating around producing pleanty of power from just a slightly reworked manifold
