My gut feeling is, in a "bracket race" 512 application there would be more difference between the two heads...... But even if there wasn't...... After the motor has already been built, where are you going to find an extra 25hp for $400?(Which is what the difference in price between the 240's and 270's is).
And the flip-side would be: what engine would be BETTER with the smaller heads. It's probably not a stroked motor.
