If you go through the traps at 6500 RPM with a 4.30 gear and a 26" tire you would be doing about 117MPH, which for a 375 HP engine with a 3000 pound car sounds about right. I would say that 4.30 is about as much as you would want to go. With 4.56 speed at 6500 goes to 110MPH and 4.88 would be 103mph.
