Is that # stamped or cast? More resembles the casting #. I believe 7006 is a basic number for transmission case. C8AP is C=1960s, 8=1968, A= originally engineered for fullsize Ford car, P=? Not a lot of powertrain items were originally designed exclusively for Mustang; a full size Ford transmission isn't necessarily out of place here. If the trans is stamped w/ the partial VIN it must match the same digits of the actual VIN to assure originality to car. There should also be a metal tag riveted to the case w/ a trans code stamped into it. Fr that one can determine application & ratios. Hope this helps.