Gutted for you
I would love to see Yum crack 200mph, but it comes down to how much you wanna throw at it. If its what you want, go for it.
I spoke to Cosworth about the alloy block, they said it was'nt aimed at engines producing very high outputs. If memory serves, the fella on the phone said 500bhp was the limit for them.
Best of luck with the car, hope it doesnt cost you a silly amount to put right.