I ran mine with 4.10 gears and a 26 inch tall tire for awhile.They were g60 M&H racemasters. It was around 3500 rpm on the highway at 55 mph. When I went to the 275 60 15 tire it dropped the rpm a little on the highway but not a bunch really. If your main concern is street cruising, go with the 4.10. If your main concern is E.T. I would go with a 4.56 because the car is a tank. If you are not comfortable with the rpm you are turning you can always go to a taller tire. JMO