I have a very good running 78 440 in my pickup. Can I get 400 hp or close without swapping pistons? I know compression is low. What can I do that will improve performance? I have headers on it now. I also have a Performer RPM intake with a 750 Holley to put on it. Right now I'm running 516 heads that have larger exhaust valves in them. I do have a set of fresh 346 and 452 heads on the shelf. Cam choices? Current set up now is an automatic, 3:23 gears, and I'm running 26.5 in tall tires.