If you don't need emissions get rid of that smog pump ... gives you some extra hp and a lil less weight. I believe you could also do something with the EGR after that but not 100% nor am I sure it'll help.
You could get rid of the AC too if it has it, that'll clear up some HP and weight as well. The best part is both of those are almost free "upgrades".
Look for an electric fan as well, I believe you can pull it out of a junk yard.
Of course to beat an LS1 ... you generally will need what everyone has pretty much mentioned already. | 
