I have an expedition that had the 4.6-5.4 swap done and man was it done wrong. The 5.4 computer won't work unless you get all the wiring ignition and insurer ment cluster o and the keys from the 5.4 donor. You can swap in the 5.4 and use the 4.6 harness and computer but it won't run 100% like it should and you'll be best off getting power hungry tuner and to write you custom tunes. If you have the 4r70w you'll need a different torque converter which you can source from a f150 that has a 5.4/4r70w. You my not need to do all the sensor crap I did since yours is a 99, but I believe you have the coil pack ignition still and the 5.4 has coil on plug. The swap is a direct thing if you got all this figured out and be sure you have the right radiator some 4.6 had a single row and the 5.4 had the 2row.
