Hy lutrexen, The stock rear end ratio is 6.17:1 which is pretty low, are you trying to get more top speed, if so I would suggest an overdrive transmission or an accessory overdrive, rather than a differential gear change. That particular rear axle housing probably has a limited number of ratio options available. You could possibly swap in a newer diff. from a diesel powered truck , which may have ratios in the 4-5:1 range, hope that helps.
