Okay i have a 383 stroker motor with a 570 lift cam and my rear end is a 10 bolt?

3.08 is great for the highway where as the 3.90 will be a real pain on the road and eat gas like crazy, I have 3.73's in my 67 chevelle and hate it for cruising on the freeway as the engine tach's 3,400 rpm at 70 mph, the best gear for all around take off and cruising is a 3.55 ratio, I wish I would have put that gear in my chevelle.