Having completely cooked my original discs in the last race, the hunt was on for a modern replacement that didn't require too much modification.
I believe that having a bit of spare time and the internet has come up trumps. Every measurement (except one) on this Mazda 626 1.6L (1982-1987) matches the measurements on my GT discs.

The only problem is that they're probably a bit too thick for the Dunlop calipers, I haven't checked this as I'm using Metro calipers and they fit perfectly. This maybe of use to a few Belletteers, as, at least here in the UK, these discs are ten a penny on E Bay

Pom bellett. Thank you for that info recon we can get them here no probe . Will try to day . Thanks again . Keep up the good work . Enjoy your posts. Gricey

they appear to be ~14mm thick. To reduce them down to 10 or so, I would imagine one would need to verify that the rotor is capable of (legally) being at that thickness after 'wear' on the original vehicle? The drawing says around 12mm min thickness though.

I 'think' from memory now that a GT rotor has the 4 mtg. holes tapped. They appear not to be.

Yes Glen, I thought their chunkiness might be a problem, and I haven't found any skinnier ones yet. Although I haven't looked that hard, because as I've said they fit our Metro calipers well.
The lack of threaded holes we've decided is no real problem, as we've gone to using Allen bolts instead.
If we come up against any hitches with this 'modification' I shall report back immediately.