This is paraphrased from the 1963 FSM page 6R-2 Clutch Operating Controls.
Disconnect clutch fork return spring.
(There are 2 nuts on the rod that pushes the clutch fork. We will call the one closest to the front of the truck nut A. The one closest to the clutch fork is nut B.)
Loosen nut A away from the brass swivel at least 1/2" i.e. move it towards the front of the truck.
Move the clutch fork push rod by hand towards the fork so that you are lightly pressing the release bearing against the pressure plate splines.
Move nut B 1/4" to 3/16" away from the brass swivel i.e. towards the clutch fork.
Release the clutch fork and reconnect the fork return spring.
Tighten nut A to lock the swivel against nut B.
Check pedal free play.
If you have done this and your clutch fork return spring is appropriate, then the release bearing should come away from the pressure plate splines. Any major wobble from the fork that remains might be coming from a worn tranny input shaft bearing or bad pilot bushing.
