I have done several Dusters with P275 / 60R 15 on a 9" rim w/ 5" backspacing or 8" rim w/4-1/2 backspacing. Standard width drum brake 8-3/4 diff with Dr Diff (1/2") offset spring hangers and offset shackles. space the front hanger rearward 1/8", no trimming of inner lip because the inner fender sticks in further inward than the lip.
