LT1's respond very well to cam swaps. Also, you could probaly pick up a set of loyd elliot aluminum heads. (www.eportworks.com
) Also, as mentioned above, the 1.6 roller rockers are a great upgrade. There are many things that you can do to them to make them go.... I have an 11 sec 94 camaro that gets 23-5 mpg on the highway.
Oh, and a last note, all the modifications are made even better with a computer tune to help. Try madz28.com