Unless you go to 4.88s, I wouldn't worry all that much about the ratio affecting your fuel economy. :thumbsup: Higher engine rpm does NOT directly equate to more gas being used, since the injectors will likely be pumping in less fuel per stroke because it's easier to maintain speed.
The best gas mileage comes from small tires with non-aggressive tread. Anything you do after that will only hurt. Maybe not much, but generally it's hard to beat stock.
Also, if you have one, please don't spend any money on a Dana 35. Invest your money into something that will last.