Anyway here's some calipers I have with their dimmesions, its a bit like bingo......
Volkswagen/Seat not sure what this is off but im lead to believe it fits a Bora
Hole spacing - 95mm

Toyota MR2 MK2 twin pot front caliper (275mm discs)
Hole spacing - 150mm

Toyota Celica GT 1994-1999 (ST202) 275mm discs
Hole spacing - 130mm

Nissan 300z 4pot Alloy caliper, sorry no pic. hole spacing is 100mm
Hope this info could be useful in trying to find a suitable caliper for the 300 series, maybe even with the addition of an adapter bracket.