http://youtu.be/q6i5eMM11G4

My Opinion, FWIW, The Allied Fighter types that had the greatest ability to adapt through the war are the Spitfire and Mustang/P-51. Followed by the Corsair and then Thunderbolt.
But the Spit and Mustang evolved into roles not even imagined when designed due to the advancement made by Rolls Royce in continually developing the Merlin. Improvements in structure of the motor and parts as Horsepower increased, Developing the Supercharger into 1st a 2 Speed drive, and then adding a 2nd Impeller on the same drive with Aftercooling adapted the engine, and role of the aircraft it was installed in, into being able to fly into the low 40,000' altitudes.
With the Mustang and its Laminar Flow Wing design the Merlin gave it a boost in Range at higher altitudes. Adding a 85 gallon fuel cell in the fuselage increased internal by nearly 1/3 and allowed the deep escort mission to Berlin and from Iwo Jima to Japan.
In Europe bomber losses were so bad that significant changes and reductions were considered prior to the P-51B with the Merlin.
I've worked on Spitfire MkIX, XIV, XVIII and XIX. The Griffon powered ones are a beast. POH sez to limit boost to 6 lbs, 18 lbs Boost is normal Engine limit (54" MP), on your takeoff till you get a bit of speed on your roll as you don't have enough left rudder to keep it straight at low speed. To help with torque on takeoff you inflate the right MLG strut a slightly higher pressure than the left.

Jim flying a display in SM969, a Griffon powered MkXVIII we had from 09 to 15, back in 2012 at New Garden Airshow.
http://youtu.be/UptYPuNgOYc

Viewed this beauty at MCK. We stopped for fuel and the lady at the counter asked if we as seen the Spitfire in the hangar. We had not but immediately went to inspect. IIRC it was A MK IX from the Texas Flying Legends Museum on its way north when an oil pressure/temp anomaly occurred. It was at MCK for a couple of months while being repaired.

Here's a short Mark 1 video. Tally-Ho

http://youtu.be/3hzI81kEUFo