If I run a 67 crank than I will be in the Open Gp or F750. Hmmm... lets see I spoke with Tim Joyce at the Mid Ohio event and he said his HD (F750) has 30 more rear wheel horsies than his well developed Triumph 750 (T.C. heard him say it). Plus my riding ability doesn't really compare to Tim's either. Also around the Loudon track I'd much rather have a 350/500 with around 35/40 rear wheel bhp that weighs less than 250lbs than a 350 pound 40/50 rear wheel bhp clunky slow turning 650/750 Triton. If I were to build a Triton it would be a 500 or most likely a Pre-Unit with a nourished crank but you still limited to about 45 hp without the crank, and after that the cases will do you in, not to mention that its only a 4 speed. If the classes were set up more like AHRMA I would definately build my self a pre-unit Triton, Brits are still my first love, and thats why I was riding a 500 Triton this year but had some technical difficulties. George I have a Triton project under way and was thinking of making an open GP such as the one you described but haven't decided which class to put it in, if you donate a Triumph motor to me I will run it.
One last thing... Bring your modern Triumph up to NHIS and I'll show you how wimpy my little 250 is.