As I understand it, the goal in selecting a final drive ratio/tire size is to pick the ratio/tire combination that will allow the engine to run at ~2000 rpm in OD at ~60 mph. What gear ratio is currently installed? Which tranny (and what is it's OD ratio, if you know)? What engine speed are you currently running at 60 in OD (if automatic, is it shifting into 4th gear)?
Unless your running a minimum of 4.56 then I'd recommend that you regear. With 9"'s of lft I wouldn't go smaller then 37's. If you keep your current tires I'd probly go with some 4.88's. By the sounds of it your still running stock gears, probly 3.73. Trust me, your going to want to regear or you'll be sorry later.
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