Well, cheapest and fastest upgrades you can do would be NOS and a computer chip or Dyno, best for your money, there are also a few small things like power adders etc... but I dont think you get your moneys worth on small things like that (power enhancement boxes etc...) also mybe chagning out your rear end to a better gear ratio isnt to much if you can find the parts or bigger point injectors would give you alittle nice boost too.

Oh can also your intake system, cold are intake and manifold, shave down the sides for smoother air flow, it can be done by yourself with some cheap house tools and helps with air flow.