The MPC does not have a listing or description of U-bolts.
The nuts for U-bolts are 7/16-14 Grade 5 flange locking nuts.
Measure the diameter of the D44 axle tube.
You may be able to find a 7/16 U-bolt to fit?
7/16 inch Diameter Round U-Bolt is Custom Bent. Pricing includes Extra Deep Nuts and Hardened Thick U-bolt Washers. Grade 5 material.
dsuban.com