Pay attention to rear end ratio and tire size when deciding which gears will work best for you. There are calculators that will tell you what road speed and engine speed will result from different combinations of rear axle ratio, tire size and trans gear. I used them to size 1st and 5th to match a 3.42 rear.
If you are going to run aftermarket gauges you do not need to worry about finding a box with the speedo gear drive. I am running a programmable AutoMeter speedo directly off of the pulse output from what I believe is a '89 S10 box. Finding a trans with pulse output is generally easier and cheaper than with the mechanical drive.
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58 Suburban
64 Camino
