HI: I am joining becasue I need some advice! I have 1997 K2500 Sub with the 7.4 liter in it. I have added a cold air intake, cat back exhaust, and Iridium plugs. I am going to add an MSD ignition this month. I really like travelling in this, it is solid, good ride, good visibility. Is there any way to get the gas milage up from 13\15 MPG? We don't use this vehicle very much except for lumber yard runs, some winter commuting and the occasional long trip. I can retire so I see myself doing a lot of travelling in the future, plus my mom is 8 hours away. So the question is what else can I do to up the MPG? I can add headers later on, would that help? One alternative I have read about is taking out the 454 (its 15 years old) and replacing it with an up to date 383 either supercharged or not. Another was to replace the 454 with a supercharged 350 fuel injected. Or should I just go for a late model K1500 and replace the stock engine with a crate engine?