My Duster has had several different gear ratio, several different converters and several different motors in it over the last couple of years. The pump gas 518 C.I. low deck street motor with a tight ten inch converter ran very close to the same(within a 1/10 on ET and .2 MPH, not enough difference to measure do to weather and different track locations) with 3:73, 3:91 and 4:10 gears using 315x60x15 M/T ET Street Radials It did seem to not pull as hard in high gear with the 3:73 as it did with the 4:10 but it ran the same time and MPH Your ratio change will be much greater than mine 4:10 divided into 3:71 = .9048 (9.5%)versus 3.23=3.91=.8260 (17.4%) was so your results may be better or worse, go try what you got and see how fast it goes Let us know your results