The Dunstall double disc front end uses standard Norton internals. Oil capacity is the same, 150 cc per leg.
Curious to know what you think of the braking on this set-up. I have one on my cafe racer and find it is no better and maybe a little worse than the stock single disc. I'm going to replace it with a single 300mm full floater Brembo with four pot caliper and Brembo master cylinder (similar to CNW) and a Hyde fork brace.