Yes most people who are putting the Gen 3 motors in their trucks are using the 5.3 b/c of the price but any LS series engine will go in w/out much trouble. Just do all your homework before jumping into the build. I've heard of some people getting between 16-22 mpg w/the 5.3 but there are factors to consider i.e. gear ratio and whatnot. You even have the option of running the efi or going to a carb set-up so the possibilities w/these engines are endless really. Hope that helps