Stock configuration is 30 spline at the hub, 27 spline at the birfied to inner axle and 30 spline at the differential. 30 spline Longs upgrade to 30 spline at the birfield to inner axle connection. I don' t know how you could tell without taking it apart. My guess is that you'd know, or be told by a previous owner, if upgraded axles were installed.
