Your present mechanical linkage pushes against the transmission's throttle pressure arm. Since you cannot easily push a rope, in order to use a cable, you will need to either route the cable to the rear of the arm or add a piece to the arm in order to change its direction. If you master all that you will still need to concoct a method to activate the transmission kick-down. Henry did it with the bellcrank that can travel past WOT and actuate the rod to the throttle lever. The easiest way in my mind to do this would be to use the "pogo stick" throttle arm from a '55 T-Bird.Seems like a lot of trouble. What do you hope to gain by going the cable route?