[Mustang_289]

Here's what runs through the EEC relay itself:
R/LG wire from the ignition switch
BK/O wire from fuseable link located on hotside of starter selenoid
BK/LG to EEC, O2 sensor, and Computer looks like pins 40&60
Red to computer ping 37 and fuel pump inertia switch(you may not need in your config)

I would recommend getting a complete wiring guide, as you've got a lot of wiring to deal with in your conversion. I don't know if there's a step-by-step guide that walks you through the steps of converting to EFI from a carb setup.