After doing some research on the "Shelby Drop"for the upper control arm of the Monty Carlo Rallye Falcons.
It was actually Klaus Arning (who designed the suspension in the GT40), who Ford tasked to look at redesigning the suspension of the new Mustang, in particular the rear to independent. The 1963 Corvette was launched with an independent rear suspension and Ford wanted to look at a design option for an independent rear suspension for the new Mustang. During this project Klaus Arning redesigned the front suspension geometry by lowering the upper control arm by 1 inch and rearward 1/8 inch. The new front & rear suspension apparently worked very well on one or more prototypes but did not get within the budget of the new Mustang and was abandoned by Ford.
Carol Shelby then picked up Klaus's design of lowering of the upper control arm for the Ford production of the 1966 Shelby Mustang but it was discontinued sometime around mid 1966.
So it looks like the first Ford prototype of this lower upper control arm designed by Klaus Arning was likely done between 1963 and 1964 prior to the launch of the new mustang.
Weather in fact it was used by Holman moody or later by Alan mann racing for the Monte Carlo Rallye Falcons is unknown... but a possibility.