Well as i am in the middle of doing this for a friend , will give you my thoughts , he has a escort cab , he has broken his fiesta turbo which gave him an ofab loom and ecu , last weekend we decided to see if it was possible to use the separate loom with his car .

I have come to the conclusion that it will be easier to use a ofac ecu with the original efi loom and if he wanted to have the amal valve fitted just add these wires into the original loom , this will make the installation seamless in as much as the ecu in within the car and the wiring is as standard.

Hope this helps