ehem.... as others have suggested... heads would really be a good way to go especially if you want to benefit from a bigger cam..... some AFRs will run you around $1100-1300 but you will really notice an increase.... a recent article from hmmm i forget where i saw i'm sure some others saw it, but they took a stock ford 5.0, put afr 165 heads on it, an intake, carb, and headers and got it to about 425 hp