The position of the fork on the rail is set. There are detents on the rail for each position; basically the slider ends up with the same running clearance in either gear.
Plenty of room for adjustment (I've never needed more, anyway). If you have insufficient adjustment range you have the wrong rail for the slider/fork combination you're using and need to get a rail with the detents spaced further apart.
I'm looking at the 1964 parts list and now that you mention it, the picture does show a very wide bolt notch. It'll be a couple months before I'm working on the transmission. Thanks for the help.
On fork adjustments, what exactly are we looking for? Sliding sleeve being centered on the clutch hub? It seems a check for clearance would be done here (in neutral) between the hub and either speed gear. Also, would any checks be made while the transmission is in gear, ie: the shift rail has three detents, is there a check for each position?
Yes, checking fork clearance in each position confirms that the correcct shift rail (or combination of parts) is being used, or if detents require modification. You do a lot of this if you modify sleeves for deeper gear engagement.
