Okay folks, forgive me for this question. Why is there a split in years for the 7.5" rear ends? Is it just the wheel studs are different or are some internals different too? Such as bearings? The reason I ask is I plan to upgrade the rear end in my 1980 Elky. Nice 350/350 drivetrain and want to do a 3.08 gear with 28 spline axles and posi unit. Anything I need to know?