THe rods I've seen usually have about 3 inches of exposed thread on the end to help with adjustment. I don't know the correct length.
When I set up my linkages I always set the tob against the fingers, adjusted the rod to hold it there, then backed off the rod adjustment just enough to give about 1/4 inch of freeplay for the tob on the fingers.
You might want to set it that way with the nut in the inner hole on the fork.
It's possible your fork is not right too. They made all shapes of them.
Look here.
http://www.4speedconversions.com/gm-forks
Also, the pivot ball for the fork is adjustable too but the tranny has to come out to set it.