Gears, gears, and gears...but yeah, what do you intend to do with the car?
There are several proven bolt-ons out there:
Gears, shifter, catback, X or H pipe, underdrive pullies, timing adjuster, cold-air-intake/new air filter & MAF...then you get into the more involved stuff like headers ($$$ for install), custom tuned chip, suspension mods and whatnot.