I agree. But 200 hp is where I'd expect a really high compression twin-plug type1 to be.
400 hp Ed? You must be joking LOL!
If there were affordable 101.6 heads available, this wouldn't be nearly as hard to do.
TF-1 case, 90mm stoke, 101.6 p&c, and a Panchito type head with 44x38 valves. All we need is CB to make the heads!