ok, 97 means you have 4.10 gears. you will be fine with 31's sir.
my 4.0 ranger has the same gears and came stock with 31's. I could squeel the tires from a dead stop if i wanted to. so you will be fine i think with a 3.0 and 31's
save up your pennies, and buy some bigger meats!!
oh, and are you 4x4 or 2wd? with 4.10's id assume 4x4