I don't know that year very well, but the later trucks not only have nut to "shorten" the rod, they have another nut at the back side of the braket to "push" the rad forward.
If you were to "push" the rad forward on the right and "pull" it back on the left, you may have it. Notice I said to "pull" it back on the left don't just rely on "pushing" on the right.
Also, are you sure the rad is in the center of the frame? have you cross measured it?
