You can do the throttle blade mod. This gives instant throttle response. Here is a video. Its a 4.3 V6, how far do you want to take this engine. Yea you can do a rebuild, change pistons, put a can in it but why. If your going to put that much money in the truck, just do a 383 stroker swap. If you DIY the exhaust, you can do it without spending a lot of money. I have 2 old school glass packs ( about $40 each) then I made my second tail pipe out of pipe I got from the junk yard, I gutted my cats, (NO thats not legal) and I have a set of Summit shorty headers on my 97 5.7L. Did the throttle blade mod, I have electric fans, High flow air filter ( you only need to replace the air filter) In the video, it says tighten them as tight as you can get them, but what it doesnt say is be careful not to brake them. Everybody says do a LS swap, and thats OK, but you will need the ECM, the wiring, and the trans from a donor truck. The 4.3L will run decent with an exhaust swap and a custom tune, high flow air filter. By doing the tune and exhaust, you should gain about 35 or maybe 40 HP. If you want more power than that, you should look into an engine swap.