not sure if the 3.38:1 rear gears that are available for the 55-59 fit the 60-66, but likely - you've probably got 3.90 or 4.11 now .... the problem is they're pretty spendy, you'd do better to find an overdrive trans, which was optional from 55 on, and would be an easy bolt in swap, the 4 speed is only useful for the granny low - if you plan on spending most of your time pickin up hay bales or something
Bill
