Hi Brian,
First of all you need to get a new adjuster and its included ball,
It is possible (just about) to remove the splitpin nut and washer on the clutch adjuster with the end cover in place
The idea is to have the cable and arm travelling through a 90 degree angle ideal position when operating
during this the adjustable pusher should wind up in as near a straight line with the pushrod as practical
If you have a 3/8 x26 bolt (old rear bicycle axle) you can fit it in place of the adjuster
Then the bolt and cable arm should be at 90 degrees when in the correct position
There should be a thread or 3 protruding through the locknut when you refit
To determine the pushrod length get all the above sorted first
Assemble up the pressure plate without the centre adjuster, then use some thing like a welding rod and slide it through until it meets the pusher on the far side, mark the length
then measure up the SRM pusher,bearing and adjuster so as to place the adjuster nicely in the pressure plate
Trial cut the pushrod a little long, and reduce as necessary
Make sure the pushrod end is trued up square, and then re harden the end
Heat to dull red and quench
John