if you're going to spend that much personally i'd look into going with a gear change. at this point i'd be betting gears would be your most noticable change. i'd have to agree with white1 also and go with 4.56's. i know you wer asking about engine stuff, but i think there is more available elsewhere.

 

My cousin has a 98 5.7 that he just lifted 6" with 35's. he said it was gutless so he put 4.56 gears in it and now it is a little quiker than it was stock with 33's. cost him $1600 to have it done at randy's ring and pinion. it was by far the best mod he has done