SOLVED:  Replaced the jerry rigged center pin bolt on the rear driverside leaf spring, noise is now gone. $2 fix, Procomp 97-380 3/8inx4in Center Pin bolt, and I have an extra now.

The noise, I believe, was from the strain on the little washers I used to space up the bolt.


Some other facts:  The axle still is cracked, but patched.  I'm still keeping an eye out for a Ford 8.8 out of a new Explorer.