[Hanuman]

I once ran Black Diamond 280mm (standard size) grooved with red stuff on the Ur giving it a bit of effort on Knockhill, after previously getting fade with standard discs and pads on G54 calipers.
It took quite a while to start suffering fade with the BD discs.

With G60 calipers, and standard discs but Green pads, the overall feel was much better. 276mm x25mm disc. No noticeable fade after several decent runs.

Now on Brembos (Boxter), with 288mm x 25mm A100 discs, it's pretty good, but hasn't been tried hard. Currently using standard Pagid discs and pads after having a bad set of Black Diamonds!

Apikol do/did a brake calliper bracket in machined cast iron, but my calipers are mounted on Ally brackets from Bambridge.

I think, but I'm not certain, that there are discs of the right size for 4 stud hubs.
On the rear, if you can find a suitable disc, the 'vented' calliper & bracket of the V8/S6/20vUR may fit, but would it give you much extra without a bias pedal box?