You'll definitely need to change that puny fiesta pump. On an MFI engine the fuel pressure is what opens the injectors - they aren't electronic. I doubt that EFi pump will have enough pressure to start properly let alone rev up.

The engine loom is totally different on an MFi. You'll need the wiring for the dizzy, coil, the warm up regulator and cold start valve and also the speed sensing relay that goes under the dash to get the pressure release valve working. Tbh - you'd find it much easier to do an EFi conversion as the loom will require fewer changes and you'll be able to keep the fuel pump etc. This is probably not very helpful if you've been given an 1600Mfi lump. In which case you'll need to unpick the Orions engine bay loom, trace it back in behind the dash and pick up the relays and splice that into your Fiesta loom.

Where are you planning to mount the fuel distributor? On the battery tray?