Rear overdrive unit interchange a500-a518-a618

Just looking for some information. Will the rear overdrive unit of an later model a518/46re (say 1997 or so), bolt onto an earlier model a500r/42rh (say 1988 or so) and work correctly ?
What about the overdrive unit from an a618/47re...will it bolt onto an early a500/42rh.
Only asking because the later a518 and a618 overdrive units were built with update/stronger parts...from what I have read ...could be wrong about that ???