Swapped to Muscle - 75 Duster Daily build

For a somewhat simplified rear end and disc brake setup, have you considered using an 8.8 Ford out of an Explorer. They are typically equipped with a track lok diff, and 3.73 or 4.10 gears, plus disc brakes, and 4.5 in bolt circle. There are several threads on here that detail the process of using one. Just a thought.
Your build is very interesting and it is really cool that the kids are interested and involved.