You should have about 1/8" of free travel of the release lever before the release bearing contacts the pressure plate. This is somewhat more at the pedal, but gives you the exact positioning of the over-center movement of the pedal/assist spring if properly adjusted. 66 and later used a fixed-length upper clutch rod to assure that this dimension would always be perfect. If you have a 65, you can always retro fit one, as long as you have the adjustable lower rod.