truckeroy,
I think the major confusion over where to place the rear axle on 1/2 ton AD trucks comes from the spring center bolt being 1-3/4" forward of the axle center line in the stock configuration. The u-bolts hold a bracket containing a rubber bushing similar to the end of a leaf spring. A matching bracket is then welded to the front of the axle and a thru bolt clamps the bracket to both ends of the bushing.
When I first converted my '49 to a newer rear end, I made up a couple of saddles from 2" x 4" 1/8 wall steel tubing and just drilled the hole for the center bolt 1-3/4" forward of the axle center.
If you have a service manual, there is a picture of the rear spring seat in the rear axle section.
