318 horsepower

the 360 cast crank torsion's/flexes at a lower rpm than a steel 340 crank does, thats all.
Factory 340 crank in my good friends circle track car would touch 9000 rpm all night as did the 273 rockers, but man would they wear valves @.620 lift.lol

it's a small diff and by itself in most cases wouldn't stand alone to cubic inch but consider the rod ratio.