Theirs some good photos of the Griffon Mustang in the book Rolls-Royce and the Mustang (I just finished the book last night!) It would have been a hell of an airplane! The mock up was made from three dismantled Mustangs as they were hoping to use as many off the shelf components as possible. The 1st mockups were built using a Merlin as the modified Griffon was unavailable.