i would go to a junkyard and pull all the parts you can that pertain to the 5.0L. I'm sure i am missing some things but here's a basic list: tranny corss member, bellhousing(a T5 from a 5.0 is stronger, you at least need the right bellhousing and special size pilot bearing), pilot bearing, motor mounts, exhaust, driveshaft(maybe), etc...it really depends if you want a carbed or EFI 5.0, many people have done the swap, if you're new to mustangs you will want to get to know the parts of the car as much as you can before attempting this, good luck
~Mark~