this maybe a stupid question but why is the intake next to the spinner on top??
I would guess for extra cooling but Im not a mechanic.
I'm looking for a goodp picture/cutaway to share with you two now. In a nutshell, in a normal late-model P-51 the air intake opening located under the spinner takes the air uner the engine through a trunk, after traveling all the way to the back of the engine, it makes a sharp 90degree turn up and travels a little ways further to the back-top of the engine, where the rather large supercharger is located. Once through the supercharger, it is fed from the top-aft of the engine to the banks/engine.... it works but is inherantly/obviously not the most effecient routing (when talking racing and getting the most outa your most) given you just took the air from the intake on the bottom of the spinner 270-degrees around the entire length of a merlin V-12.
Not the best angle, but this cutaway has fantastic detail and you can see most of what I'm describing in it.

The earleir mustangs had the intake on the top, but this was considered an obstruction and the relocation of it greatly/vastly improoved a pilots view looking forward or over the nose.