There is a direct relationship between torque and horsepower at any given RPM, as your formula calculates. However, most engines produce a maximum torque at a lower RPM than where the maximum horsepower is generated. If you calculated 29.7 as the horsepower from the maximum generated torque, then the engine should still be producing a bit more horsepower at a higher RPM.
From the figures originally quoted by Honda in their sales literature for the 350 twin, dated February 1968, they claimed maximum horsepower and torque as follows: 36 HP at 10,500rpm and 18.5 lb-ft torque at 9,500rpm. I always believed these figures were exaggerated, and what you calculated/quoted, although lower, seems more realistic.
