As japanese model cars goes, let's see,
The current mitsubishi lancer Evo series had been produced as model kits by both Hasegawa and Tamiya, though Tamiya begun production later on with the Evo V series.
Both Tamiya and Fujimi made models of the nissan skyline (all trims) at the same time. And I think so did Aoshima.
As for the 1st gen RX-7, Tamiya also did a model of it, very long time ago.
Actually, after looking at some older kit boxes, I'm wondering if Monogram actually do it's own molding, mainly because some of their models are actually reboxed Fujimi's or Tamiya's.