North American didn’t conform with producing arguably the best fighter of WW2. They knew there’s still room for improvements in their majestic P-51D. Developed via the XP-51F and XP-51G prototypes, the P-51H was a considerably lightened souped-up Mustang which achieved the stupendous top speed of 487 mph; 50 mph faster than the P-51D. In production just before WW2 ended, the P-51H came too late to see combat. A pretty number (555) were produced anyway and they served until 1952.
Magnificent photo of a “H” of the 194th Fighter Squadron, California Air National guard. At first sight, compared to the P-51D, the H had a longer deeper fuselage plus a taller tailfin.