“Best” all around axle ratio: ~450hp w/ A904?

I have a similar combo to yours, 3:91's works great but eats fuel and buzzing around 3200 at 50mph. I just changed to 3:55's . No data yet but I will post once I get the car out of winter hibernation.

Your speedo or tach are off.

2,350RPM at 50MPH.