13's are not that easy, if they were everyone would be putting down those times. If traction and all conditions are perfect it will take 355 rear wheel horsepower to move 4000lbs down the track with an ET of 13.0588, 335 RWHP to move 3800lbs at 13.088, and thats given perfect power transfer. So do you think a set of 4:10's and a 4K stall are going to do it on a stock motor with 232 RWHP?? If you do not want to spend major money NOS is your ticket, but its a crap shoot, a stock bottom end is stable to about 440HP, flogging it with enough laughing gas is a real gamble.
My wife's car latest dyno run was 372RWHP and she runs 13.5 to 13's with poor traction 3.5K stall 3:73 gears and a built motor.