We already have a Cosworth designed head on the car...
I'm not sure if the aftermarket Cosworth head (more for standard Zetec engines)
is a big enough improvement over the stock SVT head to justify the cost.
You'd also lose the VCT with that head.
That set up cost over 4 grand IIRC (I know who you're talking about). For the same price (maybe cheaper if you go DIY) you can go turbo and destroy those numbers. I may only have 31 more whp, but Im tuned low, and I would run away at highway speeds.