It is possible that the missing gib strip adjuster will be a BA thread, being Myford. You will need a new grubscrew and a nut to lock it once adjusted.
If you want to use on the Boxford, you will probably need to make a new T nut to suit.
An epic case of "Need one to make one"! Maybe for a one off, you might get away with a jury rig, (Turn a bit of bar, tap it and file two flats ) so that the end product can be used for the future.
Howard