fast or atomic efi ?

I recommend working out the fuel supply first, since you need that for any EFI system. You can easily rig it to run your carb for now by just using the ~3 psi return drop to supply the carb, and that will let you keep a carb in the trunk for emergency backup. Designing the fueling is not bolt-up and may prove time consuming. Many posts on different ways people have done it, including me.