Narrowing a Dana 60

Buy your rims/tires and mount them.
If you plan to mini tub, go ahead and do that.
Level and plumb the car.
Prop up the wheels in the wheel well to where you want them to sit.
With both wheels aligned with CL of car, and centered in wheel opening, measure inside-inside of the wheel bolting surface.
Subtract for thickness of rotors or drums.
This is your overall width of axle you want.
Narrow your housing, order axles.