Do you know what ratio you have? If you have 3.73's and you get 285/75 or equivalent sized tires, I wouldn't worry about it. But 4.10's would be ideal.
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If you don't know what gears you have look in your glove box and find the rpo code that corresponds with one of these:
GQ1 -- AXLE REAR, STD RATIO
GT4 -- AXLE REAR, 3.73 RATIO
GT5 -- AXLE REAR, 4.10 RATIO
GU4 -- AXLE REAR, 3.08 RATIO
GU5 -- AXLE REAR, 3.23 RATIO
GU6 -- AXLE REAR, 3.42 RATIO
G80 -- AXLE REAR, LIMITED SLIP (POSITRACTION)
HC4 -- AXLE REAR, 4.56 RATIO
Also if you have 4wd, you will have to swap gears up front as well, so remember to account for that if you price out some 4.10's