The differnt between wiper motor, built in up to 1987 and later to the wiper motor built-in from year 1988 is the form of motor shaft.
To see on the picture below is the cylindrical shaft of a wiper motor built-in up to year 1987. In contrast to this wiper motor the wiper motor built-in from year 1988 has a conical shaft.
Cylindrical shaft of windscreen wiper motor, used up to 1987:
