I am wondering how big is the opening in diameter regarding the original V6 Mustang airbox, that could be a benchmark for your experiments. And also, if it is the same or a similar box in the Morgan, how is the stream of fresh air directed in the Mustang. The shape of and the flow in the airbox is an important factor to insure a good intake. I would also experiment how it works when you close the original opening because - it must not but it could - happen that the air gets unwanted turbulences when the different channels meet coming from different directions and from the side vs. the bottom.
