It really all depends on the use of the car. If it's strictly street then 3.55's are the norm but if you drag race it could be anything up to 4.56 or higher. It is usually a personal choice, the person's age sometimes is a deciding factor too.
my dart is a pretty much a dedicated drag car at this point, and i can tell you with a 26 or 28 inch tall drag slick, if i had 4.56's i would be DONE at 1/8 mile.
727, with 3.91 gears, 26 inch tall tires, and my 6800 RPM shift light is on at the 1000.
i voted 3.91's and i would not go numerically higher unless i had 29 or 30 inch tall tires.
