The aircraft you are looking at is Wee Willy II, based at the Planes of Fame Air Museum in Chino, California. It does not have a straightforward history because it is not a straightforward airplane.
The airframe is a composite, rebuilt from the salvaged wreckage of the Red Baron -- a heavily modified P-51D that set the Federation Aeronautique Internationale (FAI) world speed record for piston-engined aircraft in August 1979. Later that same year the Red Baron was destroyed in a devastating crash. Steve Hinton of Fighter Rebuilders took what was left, combined it with parts from other Mustangs, and produced this aircraft. As Hinton himself put it: "It has got a lot of personality. It is just through luck and maybe that it is the ghost of an airplane."
The paint scheme and name honor 1st Lieutenant Calvert L. Williams of the 362nd Fighter Squadron, 357th Fighter Group. Lt. Williams fired the very first aerial victory for what would become one of the most remarkable fighter groups of the entire war. The 357th -- known as The Yoxford Boys -- did not fly their first combat mission until February 11, 1944. The P-51 Mustang had only arrived in England three months earlier. Nine days into combat operations, on February 20, 1944, Lt. Williams shot down a Bf-109 flying his P-51B Mustang named Wee Willie. That was the opening shot. What followed was extraordinary: the 357th went on to destroy 595 German aircraft in the air -- the highest total of any P-51 group in the Eighth Air Force.
Those four kill markings on the fuselage represent Williams total victories with the group -- he was not done after just that first kill. On February 13, 2022, Steve Hinton flew Wee Willy II in a five-aircraft Heritage Flight formation over SoFi Stadium for Super Bowl LVI -- a ghost of a world speed record holder, wearing the markings of the man who started it all for the most successful P-51 group of the war.