Based on your picture. When you install the alignment pin in the shifter the reverse lever is move rearward as compared to the other two levers . That tells me that the reverse rod would have to be longer or the shifter would have to be mounted more up right then the 68 and later shifter. The reverse rod is the most effected rod length by changes in the shifter mounting angle.
This makes some sense. Maybe that shifter will work with the 1968 and later rods and using the 64-65 mounting plate.