I don't know of a spec for that. I measured from the edge of the bell housing
to the release bearing and I tightened the nuts down until I got
that measurement from the back of the engine to the fingers
using a depth micrometer. I measured from the block because
that is where the bell housing will be bolted to. I then bolted
the two halves back together and opps there was no clearance
between the fingers and the release bearing and tat meant that
the release bearing would always be spinning when engine
was running. I was not able to back off the clutch linkage enough
to have a gap between the fingers and release bearing.
So I had to split the tractor again and loosen the nuts on the fingers.
I ended up with around 2 threads above the nuts. I was also able to put the cotter
pins in. The nuts on your plate are right on the edge of
coming off. I am surprised they didn't come off.
All of the new pressure plates I looked at were adjusted with one to 2
threads showing above the nut. I would tighten yours until you
had at least 1 thread but no more than 2 threads above the nut and at that
point you should be able to see the holes for the
cotter pins.