The car with the #15 meat ball is not the same as the "winged" version. The # 15 clearly has the offset "stacks" indicating a tunnel port 427. The "winged car" has equal spaced stacks indicating a 494 or calliope engine. While J10 has many known drivers , NONE of them raced the car as a GT40 MK IV , because it wasn't until converted as the above information states. "To me" that is VERY mis leading and is likely what hurts the value of this car. A similar action would be using a real 289 Cobra to "build" the 7th , 8th , 50th Daytona coupe LOL.
While not in the same category as the "modern run" of MKIVs done by Mike Teske , J10 simply wasn't a MKIV when built.
Just this grumpy old man's opinion.