Dana 60 too narrow

Took the measurements for backspacing, looks like I have very close to 4 inch to the frame rails and 10.5 to the wheel well lip.
With a 12 inch wheel I think 3 inch backspace and that would put 10 out to the wheel well lip.
For a total 13 inch width, sound right ?
Inch of clearance outside & an inch for the inside.
Thanks