From Nick Lappos post in Megan's link
The later model 76's use the 107 Nr exclusively, mostly for high speed maneuver effectiveness, and also for tail rotor effectiveness at low speed.
and
Right on, Stan. The extra Nr in takeoff has an advantage if a landback is made, due to the extra rotor energy as S76heavy alludes (to be exact, the inertia is the same, but the stored energy is higher).
When trying to hover and engine temperature limited, it is better to be at lower Nr. If torque limited it is a wash, just as you say, Stan.
Increasing Nr on a twin to improve OEI performance is normal practice.
That doesn't answer the 407 question though.