[jhv48]

With that much horsepower, I would run around 3.25 in the rear and change out the OD fifth to a more friendly number. If your powerband will allow it.

Mine runs about 2200 rpm at 80 MPH with a 3.73 rear end and a .64 OD fifth.
Would prefer a .82 OD as fifth gear is close to worthless if you don't want a 3000 rpm drop between fourth and fifth!

Great for cruising the freeway and mileage though if it doesn't fall outside of your powerband.