Yes, 318 is the horsepower on an 8v71N commonly used in trucks. With brown tag N65 injectors if I recall correctly.
There are many many other horsepower ratings for the same engine depending on injectors, turbo, or turbos, aftercooler, RPM, and other things.
Anyone seriously interested in Detroits should find a copy of a "Field Service Data Book", a small notebook printed by Detroit with all kinds of good info including HP ratings for different engines.
