The question on my mind is why do you want to do this? The plane was designed for the engine to be in its place, so why mess with it? A change in engine location that drastic will also probably cause fuel feed problems, notably flooding at idle and fuel siphoning into the engine while it isn't running. That's assuming the plane was designed with the tank in the right place to begin with.

So what's your reason for wanting to change the engine mount location?