I can partially answer that! The later MK2's had single pickup, can't remember if the switch was '89 or '90.The only change was substituting just one pickup instead of 2, and different TCI. Other than a change in the front suspension not related, that's pretty much the only difference. Maybe they should be called MK3's.
I know Gary makes up the aftermarket TCI's for the later MK2's as well...