I also got just shy of 75rwhp from a 2 valve Triumph, but it was 840cc and had squished heads and etc.
The 906cc wasn’t really a Triumph per se, it was a Nourish in Triumph unIt cases, albeit extensively welded and strengthened, 80.5mm bore and 89mm stroke, 180 degree crank, Dresda cam timing (based on Z cams but with more duration), 38mm carbs and ports, 11.5:1 CR, blah, blah. A very quick bike.
Actually, IIRC, although it did produce 84bhp on the dyno, that’s not how I raced it. For some reason that I don’t understand, with 1000 series mk1 carbs it produced a much fatter torque and power curve than it did with smoothbores. Whilst the 1000 series carbs produced less peak power, the overall power and torque characteristic were better. I think in this set up it produced 79bhp and that’s how I raced it.