Info on a P-51 mustang called "Spare Parts"

I am trying to get some information on a P-51 mustang called "Spare Parts".
My wifes grandfather worked on this plane while he was in WWII. Said it was
his favorite airplane. He was a mechanic and help build this plane from
three that were damaged. I am an amature artist and would like to make a
drawing of the plane for him. Any information about this airplane or
flights would be helpful in putting together a historically accurate sketch.

thanks in advance for the help.