Dynamic,
Lots of reasons why it was not produced on a 76:
It never went into production because we didn't want it to, it wasn't designed to do so, it was a flying wind tunnel for Comanche.
It was much heavier, at least 50 lbs, than a tail rotor
It has more drag, about 2 square feet total, which reduced speed and range
The Fan had to be on the tail shaft centerline, or the weight would be even higher with an intermediate gear box. That meant that the nose up angle for touching the tail went from 15 degrees to 6 degrees. That would have required the tail bumper be qualified as a normal landing point, making the weight even more once the tail cone was stiffened.
It wasn't needed, unless S-76 people needed to go sideways ay 100 mph!