Re: borg warner diff.
Early BW in falcons are 75 series (7 1/2") gearsets. From EA or EB onwards they went to 78 (7 3/4") series gearsets, right through to AU. Early will go into late, late will not go into early. Mental note to self, don't get whoever told you that to build a diff for your car.
If you're not driving a manual you're really just steering.