I've seen a few RC Cobra CB750's (one of the SOHC4 members here had one) and I doubt that RC built that bike, yeah, I know it's got an engraved tag that says "RC Engineering" etc, but RC were engine builders, and all the other RC's I saw were all about the engine, and I can't ever remember seeing one with Dunstall bodywork.
More likely someone bought an RC Cobra-engined bike, and added some Dunstall bodywork. The whole thing looks a little "dated" to me though, isn't it funny how when we were young, we all though that the Dunstall bodywork was really cool, but nowadays, the original bike actually looks better?
Geez, I hope that's not maturity sneaking up on me, next thing I know I'll be sitting out in front of my local Safeway store, telling stories about the "good ol' days", ha ha! Cheers, Terry.