If you do the 3800SC swap, you'll gain 100 hp. With a few mods you can get an increase of 200 hp. The swap without mods will run you $2500 just in parts and labor with you furnishing the car and engine, tranny, wiring harness, axles, and computer. A 3800NA will get you an increase of 65 hp. I think the 4.9 will get you a gain of 70 hp. And the Northstar I think it's 160 more hp. Or you can do the 3.4 and get 20 more hp. The 3.4 is the cheapest swap.