340 4 barrel and 340 6 barrel: were they really UNDERrated?

I remember reading an interview with a retired Chrysler dyno operator who stated that he had never seen a 340 that made less than 320 horses.
Here's my reasoning for why Chrysler rated them at 275 hp.
First off, insurance companies were charging much higher rates for any cars that were rated over 300 hp, which discouraged sales. Secondly, when the 383 was rated at 335 hp in a b body, how much would the a body sales have cut into the b body market if they were advertised as 320 hp in a Dart? Smaller, lighter, and less expensive than a b body?
They weren't going to cut their own throats and kill sales of Chargers and Super Bees by doing that, so the 340 got rated as 275 hp @ 5000 rpm, which was probably fairly close, but push it to 6000 rpm and hold on!