You will need new suspension, rear axle, tranny, engine and tranny mounts, radiator, harness, misc small things, MAF, and what you forget and remember when you need it.
Well, basically same thing as a 4.6 swap generally speaking. However if you go to the 4.6 boards there is some info about 5.4 swaps. I've looked into this for the GT and there is a company that creates 5.4 swap kits. Basically it's pretty routine for a swap but you will need to modify the stock hood or get a new one.