It's a tweak to the chassis that is inherent in the design.
The M34 and M35 were companion models with the only major difference being the bed and the rear duals or singles. The conversion, insofar as the duals/singles is concerned involves flipping the hubs around with the same bolt holes that the drum attaches with being the same as the bolt holes for the axle half shafts. The bearing races are the same inside and out.
The reason for the singles gives higher road speeds, less unsprung weight, 1100s have higher load bearing capacity and a bit more ground clearance. Off road you're running the rears in the same path as the fronts so you're not making another channel in the mud after the front's have pushed their channel. So, you're better off getting through the sloppy stuff.
Edited by rmgill, 18 January 2018 - 1037 AM.