Get all new sensors, actuators, and wire harness. Find some way to verify the computer is functioning properly. Finding someone who understands how EFI works with the engine components themselves will prove invaluable.
I tried putting a 1989 5 liter into my Galaxie and came away with nothing but trouble. When running the car, I could drive some place and love it. Then get back in the car for the trip home and limp all the way. The inconsistency (I later learned) was due to the wire harness being old, connections not being as solid as they should have been, and the OBD1 setup wherein any sensor failure registers as a total system "limp home" failure. Any time I wiggled one connector, it would move another and it was a complicated game of where is the trouble this time?
I still like the idea of EFI, but have switched to a 331 and carberator for the time being.