In my '55 Bel Air I have a 292" six & a std. trans. with a top O.D. ratio of 0.73. Behind this I have a 3.08 axle gear & 205/75/R15's. This is in my daily driver, avg. 12K. mi./yr. Only real way to know on your own is run it & experiment. I have 3 other ratios, all lower, that I've ran in past years but this works good for me. If you get to a place where top gear is too high, downshift. If low gear is too high, its definitely time for a change. Doug
