LS1 or Work on the 4.3L??

I have myself a 98 Blazer, 4WD...Ok heres the thing. I lost on what to do. I want some speed. So its either gonna be dropping an LS1 into it, to stay emmisions legal or im just gonna work on the 4.3 in there now. Which is the better idea?? I can buy an LS1 with 6 speed tranny and have it shipped to my door for 3,000 dollars and lets say about another 1000 to drop it in, so about 4000 altogether to have an LS1 in my Blazer orrrrrrrrr i could take that 4000 dollars and throw it into the 4.3L...Will i get more power by doing the work with all the money to the orginal motor or will i still get more power and speed from the LS1...Which way should i go here?

i would drop in the LS1 myself