Here's a chart that will allow you to get the proper speedometer gear from Jeep if you have the older gear driven speedometer. I used it for my '93 ZJ and it made the speedo very accurate.
R&P/Tire: 33" 32" 31" 30" 29" 28"
3:07 SG26 SG27 SG27 SG28 SG28 SG29
3:55 SG31 SG31 SG32 SG33 SG33 SG34
3:73 SG32 SG32 SG33 SG34 SG34 SG35
4:10 SG34 SG35 SG36 SG37 SG38 SG39
4:56 SG36 SG37 SG37 SG38 N/A N/A
R&P/Tire: 33" 32" 31" 30" 29" 28"
3:07 SG26 SG27 SG27 SG28 SG28 SG29
3:55 SG31 SG31 SG32 SG33 SG33 SG34
3:73 SG32 SG32 SG33 SG34 SG34 SG35
4:10 SG34 SG35 SG36 SG37 SG38 SG39
4:56 SG36 SG37 SG37 SG38 N/A N/A
