This is Doubleknit Doon -- I think N100DD. Soon after purchased by Jack Sandberg and raced for several years at Reno and Moose Jaw as Race #28, with Chuck Hall and Gary Levitz as pilots. Later owned by Levitz as Miss Ashley in red and black civil paint scheme, raced as #38.
This Mustang is most probably 44-74923, with the civil registration N5438V until 1969, when it was sold to the Fuerza Aerea Salvadorena and became FAS-410. It returned to the United States in a container in 1974 and became 44-11353a. It was rebuilt by Dave Clinton and Don Anderson and was registered as N100DD in 1978. Your photo shows the plane with the letters I-DD on the fuselage. It later flew as "Miss Ashley", a red racer, with #38.