Shortround6
Major General
A lot of what you say is true, however.Also, the Spitfire took on roles, like long-range, high-altitude PR, that the Mustang never fulfilled.
Just US service
F-6A...........................55 converted...................................................1942 modified P-51-1
F-6B...........................35 converted...................................................1943 modified P-51A
F-5C...........................91 converted...................................................1943 modified P-51B & C
F-6D..........................136........................................................................Nov 1944 Recon P-51D
F-6E...........................161........................................................................April 1945 Recon P-51K
Early planes carried two K-24 cameras.
Merlin powered versions carried one K-17, one K-22 and one K-24.
I expect a few variations from that
One camera port oblique behind the pilots seat and the other one was vertical in the underside.
The K-24 Cameras may not have given the definition wanted at high altitude,
The K-17 and K-22 cameras were larger, used bigger film and had longer lenses.
Mustangs may have been late or in small numbers but they could perform the role.