When installing one piece U shaped spring shackles used on 23-27 T's, is there a right way or a wrong way when inserting them into the spring and perch bushings? The Ford Service Manual shows the shackle inserted into both the front and rear spring, so that the shackle bar, castellated nuts, and cotter pins, are facing outward toward the front of the rear of the vehicle, depending on which end your installing them on. This would certainly make tightening the nuts and installing the cotter pins easy. If that is accepted way, I just never noticed to look on my unrestored fordor before I sold it.
In the Ford service manual, page 170, figure 376, you can see a clear picture of the bar and nuts of the shackle on the rear side of the front axle. Hope this helps.
Page 168, figure 370 gives even a clearer picture showing the shackle bar, nuts, and cotter pins on the back side of the front spring and perch. Page 17, figure 54, shows a mechanic removing the rear shackles from the rear spring and the shackle bar, nuts, and cotter pins face the rear, so regardless of which axle you were working on, the shackles must have been inserted from the front with the bar, nuts, and cotter ins facing the rear, as I see it.