"A car having a final drive of 2.98 and a direct 4th gear has the same overall ratio as a car with a .80 overdive 5th and 3.73 final drive. The car with the overdrive will use more horspower and generate more heat thru the transmission, then the direct drive box. However maybe the 3.73 rear may offer more low speed punch on turns."
took this from near the bottom of the page ---->
http://www.5speeds.com/ratios.html
this is kinda a different answer than your looking for i think... but it sheds light in that area...