I've been away crashing my bike
(Diesel spill in conjunction with too much speed / lean for conditions, but I'm ok).
So now I'm rebuilding the bike into the racer sooner than I thought.
Below are the discs I plan to mount (somehow) and they are 5 bolts like the original discs. They are also almost the same size as the wheel
However, I've decided that I'm going to run 18" wheels off a 1987 Suzuki GSX-R 750. Those may be a challenge in themselves to fit, but when I do, it'll mean I can run some fairly decent modern rubber (been looking at Dunlop Roadsmarts 120/70 front and 160/60 rear).