gutless gas hog 5.4

[navistardiesel]

i got a gutless 5.4 e150 van. its also a gas hog. my father had an 88 f350 with a 460 overloaded and it got better mileage that this van. the vans overloaded, but i need to get more power out of it, also could i put e350 springs on it? would that beef up the suspension. i need more power out of it, since the mpgs are already down the toilet