You have a 14K-18K chassis, the trackbar for this model does not bolt to the differential, it attaches to the rear swaybar bracket. I am attaching a link for Brazels and the Ultratrac rear trackbar for a 29M. Hope this helps!
UTF53V8R - Rear UltraTrac Trac Bar Ford F53 14-18K GVW Chassis (Fits V10 & V8)
If you look at the page there is a PDF of the installation instructions you can look at.