The way I'm looking at the picture that bolt looks like it goes through the bushing that goes inside the differential. Part no 3 in the above picture.Looking it up on tascaparts.com, PN is
W710443-S439
It won't be listed separately since the UCA, mount, and bolt are sold as an assembly.
That's what I thought. Local ford dealer just confirmed that. I'm at ace hardware now trying to see if something works.