you'll want a GX manifold, as these had the twin 38 Hitachi SU's standard. Lynx or Redline make one as well, but I think it's only round port. I modifyed one of those a few years ago to suit the oval port A14 head when I upgraded from the A12. Just a simple cut and shut onto the standard A14 manifold just before the split into the separate runners for each port. A clean up with the angle grinder after having it TIGed and your away.

http://datsun1200.com/modules/myalbum/photo.php?lid=619

ps - the Sports2000 had twin sidedraught Solex (Weber style) carbs.