Jim,
Just so you know, when changing the color of a car, it's best to do it when the engine is out.
I am assuming that you will no doubtedly want to show off that hott new engine. If you do that, in my opinion, with a different colored engine bay or one that hasn't been shot properly(i.e., engine and all still in it), it would not look the best it could.
Just my $.02 and experience growing up in a body shop.
Mike