I done this conversion on my Zetec s .
I has a whole car to strip from which was lucky, I used a analogue loom , which made it had work as I had to swop everything , then the rear end need rewiring as all plugs where different there where some otherthings that I had to swop , by using the whole loom you lose your fog lamps , so I rewired them in with the high beam .
But I you use the digital loom you only need the wiring under the bonnet ( plus the odd wire in the car ) but then it is as good as plug and go , if I remember right
You need

Engine ( of course lol)
Dig" engine loom
Air flow meter
Ecu
Keys

That what I found out after the convertion , also if you don't use dig" car loom then you need to change the fuel level sender as a full tank will read empty , and reversing the wires don't work , and the sender was not a direct fit in the tank , but I think the puma tank may fit , but I didn't try it ( I should have )