Well being that you have an auto, you can see great results from a 3000-3400rpm Stall converter and Valve body (jerry mod its free if you know what youre doing). Also cant go wrong with some gears. Get at least 4.10s!! You wont regret them! Since you have a 98 you may also look into getting some PI (99+ SOHC) Heads and PI intake. Top that with some VT Engines Stage 2 N/A cams and you should be around or a little over 280rwhp with a good tune.
Keep in mind these mods arent cheap and you can see better results in going Nitrous or Forced Induction.