Uhm.. remember that HP alone don't give excitment.. so the most important part is not the engine, but the chassis. And about the chassis beeing based on the real Diablo plans, well, IMO the result will still be leagues from the real thing. If people could really build an exact replica, I'm sure we would see many more replicas around.. a supercar is done by thousands of small details and I'm sure that even a perfect replica with every single small bit exactly replicated, won't come close to the real thing.. not to talk about the "aura" that the replica will enver be able to replicate, but still, if there are people that still loves to spend the money a normal person will spend on a house in their supercars, it's because there is something special in them, not only the status symbol, but well, the thousand of manhours put into them, the passion of all the people involved can't be simply replicated thanks to some sheet of paper IMO

And BTW, your project seem to be quite an expensive one. For sure not like a second hand Diablo, but not really "cheap" since you can't really build a chassis from zero for free if you want a good one, not to talk about buying the original suspensions and so on...